Author Topic: D.H.88 Comet Follow-Ons  (Read 2302 times)

Offline apophenia

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D.H.88 Comet Follow-Ons
« on: June 30, 2021, 08:40:05 AM »
Fast Air Mail - the de Havilland D.H.88 RM Comet Mailplane

After a highly successful showing in the 1934 MacRobertson Race, there was great interest in de Havilland's twin-engined D.H.88 Comet racer. The French government bought one of the three racers - G-ACSR which was modified as mailplane F-ANPY. The French then ordered another Comet, F-ANPZ, built from the outset with a mail compartment in its nose. Not to be completely outshone, the Royal Mail belatedly followed suit. In early 1936, four purpose-built D.H.88 RM Comets were ordered from de Havillands.

In general configuration, the General Post Office's Comets were similar to France's F-ANPZ. The racer's 128 Imperial gallon fuel tank was deleted and replaced by a hinged-top forward-fuselage mail compartment. Although advised to make minimal changes, the General Post Office slowed delivery with modifications. For its 'Domestic' variant - the D.H.88 RM 'D Type' - the GPO insisted on omitting the navigator's position in favour of an increased mail capacity. This would prove unwise ... beyond incurring delays.

Another result of 'D Type' modifications was that the less-heavily modified 'Airmail' variant - the D.H.88 RM 'A Type' - would be delivered to the GPO first. The D.H.88 RM(A) remained a two-seater. For longer-range international airmail flights, the navigator was deemed essential. This reduced mail capacity by 120 lbs - the 'A Type' having no aft mail compartment'. However, pilot's generally regarded the D.H.88 RM(A) as having better handling than the single-seat 'D Type'.

Top De Havilland D.H.88 RM (A Type) Comet mailplane, G-ARML. The swiveling tailwheel was part of a 1938 upgrade programme.

Royal Mail livery for the Comet was all-over 'pillar box' red except for a black 'cheat line' along the top of the nose. [1] Markings consisted of the Royal Cypher and 'Royal Mail' titles in gold on the nose; British registration letters in white; and the Royal Mail Lines pennant on the tail fin. [2]

GPO Comet mailplane service began in the Summer of 1936 with G-ARML. After proving flights to Paris and Brussels, the first 'operational' flight was made from Croydon to Lisbon where 'late post' was delivered to the Royal Mail Lines' RMS Asturias before she steamed off to South America. [3]

With a range of just under 1,300 miles, the D.H.88 RM(A) had less than half the reach of the Comet racers. However, this was more than adequate for 'Continental' airmail routes. Lisbon was a 985 mile flight from Croydon. Most routes were flown in stages. The longest was the UK-Egypt route which was normally flown in four stages - Marseilles (625 miles); Bastia (Corsica, 204 miles); Malta (515 miles); and Alexandria (955 miles). The object of this routing was to avoid Italian airspace forbidden to British-registered aircraft. A variation on the UK-Egypt route was Croydon- Paris-Bastia-Malta-Alexandria. Other, locally-based aircraft flew the airmail on to Cairo for distribution.

While the international routes were considered a success - and a boon to British prestige - the 'Domestic' variant was another matter. Demand for 'internal' airmail proved quite limited - in most cases, rail delivery being almost as fast. After a few trial flights, D.H.88 RM(D) G-ARMA was put onto a new Croydon-Dublin route. By the Summer of 1937, the Dublin service was abandoned. G-ARMA was then used as a dedicated courier service for diplomatic mail to Berlin (580 miles from Croydon) and Rome (890 miles). These 'diplomatic pouch' flights continued until the Autumn of 1938 when Imperial Airways took over this service.

Top De Havilland D.H.88 RM (D Type) Comet mailplane, G-ARMA. Note the single-seat cockpit, rear fuselage hatch for additional mail, and revised cowlings. Also visible here are the DH-licensed Hamilton-Standard propellers distinct to the 'Mail Comets'. These metal-bladed, variable-pitch Hamilton-Standard types replaced the Ratier props used on earlier Comet.

Experience with the 'D Type' G-ARMA convinced the GPO board that the second airframe should be completed as a more utile D.H.88 RM(A) model. As a result, three 'Airmail' variants were built - G-ARMB (begun as a 'D Type'), G-ARMK, and G-ARML. Ironically, the 'Domestic' role was reprised during WW2. All three 'A Types' were employed delivering priority war correspondence around the British Isles. Although not impressed by the RAF, the wartime Comets worn khaki paintwork. The sole 'D Type' was robbed of parts to keeps its siblings flying. This fairly thankless tasking was also a hard slog. None of the 'Mail Comets' would survive the War.

_______________________

[1] This 'cheat line' is sometimes mis-characterized as an 'anti-glare' panel. In fact, this paintwork was gloss black.

[2] Technically, the GPO's Comets fell under the control of the Royal Mail Lines Ltd.

[3] This allowed RML ships to take on mail posted 2 days after the vessel had left Southampton. Flying time to Lisbon at 220 mph was only 4.5 hours (although aircraft sometimes stage through Bordeaux). In this way, post from both the UK and Portugal could be delivered via RML to Brazil, Uruguay, and Argentina.
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Offline elmayerle

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Re: D.H.88 Comet Follow-Ons
« Reply #1 on: June 30, 2021, 11:47:29 AM »
Very tasty!!  Lead me not into temptation.

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Re: D.H.88 Comet Follow-Ons
« Reply #2 on: July 01, 2021, 02:38:42 AM »
 :smiley:
All hail the God of Frustration!!!

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Re: D.H.88 Comet Follow-Ons
« Reply #3 on: July 01, 2021, 02:43:53 AM »
I am tempted to do a RAF one.  Would probably be armed with 1 20mm cannon and a pair of .303 MGs.  Idea would be for it to play the role of long range/long endurance 'heavy' fighter alongside the likes of the Gloster Gladiator. 
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Offline robunos

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Re: D.H.88 Comet Follow-Ons
« Reply #4 on: July 01, 2021, 05:03:23 AM »

GPO Comet mailplane service began in the Summer of 1936 with G-ARML. After proving flights to Paris and Brussels, the first 'operational' flight was made from Croydon to Lisbon where 'late post' was delivered to the Royal Mail Lines' RMS Asturias before she steamed off to South America.



Of course, if the overseas version was floatplane, the floats could carry the displaced fuel, restoring the range, and the aircraft could alight in the harbour. or even deliver the mail to the ship while at sea, conditions permitting . . ;)




cheers,
Robin
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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #5 on: July 01, 2021, 09:41:18 AM »
Very tasty!!  Lead me not into temptation.

Sorry Evan. 'Lipstick Red' is temptation, by definition  ;)

Of course, if the overseas version was floatplane, the floats could carry the displaced fuel, restoring the range, and the aircraft could alight in the harbour. or even deliver the mail to the ship while at sea, conditions permitting . .

Good points! I did wonder about floats ... maybe extending the route from Alex to Bombay? And there's always the pressing need to show Lufthansa how catapult airmail should really be done!

I am tempted to do a RAF one.  Would probably be armed with 1 20mm cannon and a pair of .303 MGs.  Idea would be for it to play the role of long range/long endurance 'heavy' fighter alongside the likes of the Gloster Gladiator.

Oh no! I can feel an armed Comet variant coming on. Cannot. Make. It. Stop...  :o
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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #6 on: July 01, 2021, 09:43:38 AM »
Sow's Ear or Kindling? - The Fate of the RAF's De Havilland DH.88 Comet

After its success in the MacRobertson Air Race, a single de Havilland DH.88 Comet was purchased by the Air Ministry in June 1935. Formerly 'Grosvenor House' (G-ACSS, c/n 1996), the little racer was repainted painted silver overall and assigned RAF serial K5084. Evaluation of the D.H.88 was performed by the Aeroplane & Armament Experimental Establishment (A&AEE) from RAF Martlesham Heath. However, in September 1936, K5084 was written-off in a heavy landing at Martlesham Heath. In this accident, the Comet's undercarriage collapsed and the fuselage of was ruptured as the main fuel tank broke free.

Seeing no real military role for the delicate D.H.88, the Air Ministry recommended selling K5084 for scrap (estimated value being between £200 and £350). However, some A&AEE staff advocated rebuilding the damaged aircraft as a test bed for prone-pilot operation. A basic concept was draughted which involved replacing the shattered forward fuselage with a new prone cockpit section. The original cockpits were to be eliminated, the forward position to be occupied by a new fuel tank.

As sketched, the new prone cockpit would be quite cramped. (Indeed, the position was so tight that some instruments had to be mounted externally - including engine instruments attached to inner cowlings.) The pilot would lay on a 'settee' with a small Perspex 'dome' providing forward vision. It was thought that the view to the sides would be extremely poor but this was judged acceptable for an experimental aircraft. There were small 'porthole' side lights let into the canopy's hinged hood but these were more for illumination than vision.

With rough plans in hand, enquiries were made of de Havilland Aircraft about having K5084. Hatfield was appalled by the A&AEE's scheme and declined to have anything to do with it. The remains of K5084 lay in a shed at RAF Martlesham Heath while the Air Ministry cast about for a 'Plan B'. In the meantime, de Havillands made clear that they had no objection to any modification work being performed 'out of shop'.

(To be continued ...)
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Re: D.H.88 Comet Follow-Ons
« Reply #7 on: July 02, 2021, 02:11:27 AM »
 :smiley:
All hail the God of Frustration!!!

You can't outrun Death forever.
But you can make the Bastard work for it.

Offline Robomog

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Re: D.H.88 Comet Follow-Ons
« Reply #8 on: July 02, 2021, 09:25:02 AM »
Theres a lot of really inspiring stuff here,   love it !!


Hmmmmm  float plane version thats food for thought.


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Offline Buzzbomb

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Re: D.H.88 Comet Follow-Ons
« Reply #9 on: July 03, 2021, 07:38:37 AM »
Nice work.
The Airfix  Dh-88 must have been one of those kits that nearly every modeller of a certain age must have done at some stage

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Re: D.H.88 Comet Follow-Ons
« Reply #10 on: July 04, 2021, 01:17:57 AM »
Nice work.
The Airfix  Dh-88 must have been one of those kits that nearly every modeller of a certain age must have done at some stage

Nope.
All hail the God of Frustration!!!

You can't outrun Death forever.
But you can make the Bastard work for it.

Offline jcf

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Re: D.H.88 Comet Follow-Ons
« Reply #11 on: July 04, 2021, 02:48:50 AM »
DH.88 PP, the Chiropractic Special.

 ;D :icon_fsm:

“Conspiracy theory’s got to be simple.
Sense doesn’t come into it. People are
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actually is than they ever are about
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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #12 on: July 04, 2021, 03:10:21 AM »
DH.88 PP, the Chiropractic Special.

"It's just this crick in me neck, Doc ... "  ;D

Nice work.
The Airfix  Dh-88 must have been one of those kits that nearly every modeller of a certain age must have done at some stage

Nope.

"The Airfix Dh-88 must have been one of those kits that nearly every modeller [other than scale absolutists] must have done at some stage."  ;)
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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #13 on: July 04, 2021, 08:44:16 AM »
'Plan B' - Arthur Hagg is Reacquainted with his Creation

In early 1936, Arthur Hagg left de Havilland Aircraft to pursue his passion - boat building. [1] Hagg had set up his own shipyard at Walton Bridge near Shepperton in Middlesex. Hagg's new Walton Yacht Works submitted one of its designs to the RAF as a new fast tender type. This seaplane tender concept was awarded a prototype order but this contract came with a 'rider'. The Air Ministry had seen an opportunity to reacquaint Hagg with his most famous aeronautical creation - in the form of the RAF's ruined Comet K5084 airframe.

Renewed design work on the D.H.88 Comet was certainly outside the quotidian for Walton Yacht Works. But Hagg was not averse to further aviation work - indeed, he just become a consultant to D Napier and Son, Ltd. [2] Accepting the D.H.88 assignment meant taking on two distinct redesign contracts. The first was assessing whether the A&AEE's prone-pilot testbed concept was feasible. The second was a study for a much faster, single-engined redesign as a possible land-based mount for a revived RAF High Speed Flight. Hagg elected to address the more challenging, single-engined rebuild first.

The Need for Speed - RAF High Speed Experimental Flight

The new High Speed Experimental Flight (HSEF) was being formed under Squadron Leader Sidney N. Webster, AFC - raised to (T) Wg Cdr for his new command. Whereas its namesake had been aimed at the Schneider Trophy, [3] the new High Speed Experimental Flight would be dedicated to introducing higher-speed flight to service pilots. The thin wing of the D.H.88 suggested its suitability for 'pushing the envelope' on high-speed flight without the compromises of pending service types like the Hawker Hurricane. With his new Napiers connection, Hagg chose the high-powered engine he was most familiar with - the Napier Lion. Although rather dated, the Lion W-12 engine was readily available unlike the still largely experiment Rolls-Royce PV-12 V-12.

Arthur Hagg produced two High Speed concepts fairly quickly. Both eliminated the Comet's underwing nacelles and introduced a single-seat cockpit under a sleek, forward-sliding canopy. [4] The first design represented a near-complete redesign of the airframe. The formerly low-set DH.88 wings were repositioned as mid-mounted. New engine bearers (attached to the undersides of the wings) extended forward to support a geared Napier Lion. Above the wing was a new main fuel tank. Below the wing were attachment points for a new, retractable main undercarriage. A retractable and neatly-faired tail wheel was also introduced.

Hagg's Hotchpotch - Contrasting Comet Concepts

Walton drawing staff dubbed this first design the 'DH.88 (HSH)' - for 'High-Speed Hagg'. The mid-positioned wing allowed the main landing gear to be retracted up into the sides of the lower fuselage. The wings themselves were faired into the cowling extension from the W-12 Lion's lower pair of cylinder rows. This, Hagg had concluded, was the ideal aerodynamic layout for the airframe. The trade-off was in visability from the rear-placed cockpit. The sliding-canopy allowed the pilot to look past the wings (and engine cylinder side fairings). Persepx windows were also let into the fuselage belly to give the pilot some degree of downwards vision.

The second design was regarded as a back-up scheme by Arthur Hagg. The basic low-winged arrangement of the D.H.88 airframe was retained. Powerplant options were the geared Lion offered in the first design or an ungeared derivative of the Sea Lion boat engine (the latter being an attempt at cost savings). Removal of the original wing nacelles presented the problem of how to incorporate a retractable undercarriage. The wing, it was judged, was simply of too thin a profile to accommodate a sidewise hinged main gear. Hagg's solution was to install streamline fairings into which the main legs would retract. This solution paid a penalty in increased drag but allowed for a much simpler style of main undercarriage compared with the first design.

(To be continued ...)

______________________________________

[1] Hagg's former position as Chief Designer of de Havilland Aircraft would be taken over by Ronald Bishop.

[2] This consulting was as much about maritime applications for Napier's Sea Lion W-12 engine. However, Hagg would also later be involved in the preliminary design of the Sabre-powered Napier-Heston Racer.

[3] Based at RAF Calshot seaplane base near Southampton, the original RAF High Speed Flight had been disbanded once the Schneider Trophy had been secured in 1931. The new High Speed Experimental Flight would be land-based at RAF Martlesham Heath in Suffolk.

[4] In aerodynamic form, if not construction or operation, the shape of this canopy anticipated Hagg's work on the later Napier-Heston Racer.
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Offline jcf

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Re: D.H.88 Comet Follow-Ons
« Reply #14 on: July 05, 2021, 06:42:23 AM »
DH.88 PP, the Chiropractic Special.

"It's just this crick in me neck, Doc ... "  ;D

Nice work.
The Airfix  Dh-88 must have been one of those kits that nearly every modeller of a certain age must have done at some stage

Nope.

"The Airfix Dh-88 must have been one of those kits that nearly every modeller [other than scale absolutists] must have done at some stage."  ;)

"The Airfix Dh-88 must have been one of those kits that nearly every modeller in the English speaking world outside of the US [other than scale absolutists] must have done at some stage."  ;)
 ;D :icon_fsm:
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Sense doesn’t come into it. People are
more scared of how complicated shit
actually is than they ever are about
whatever’s supposed to be behind the
conspiracy.”
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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #15 on: July 05, 2021, 08:31:28 AM »
Fair comment   ;D  Now here's another 'Chiropractic Special' ...

'Haggiography' - Lying Down on the Job in Walton-on-Thames

The first part of Arthur Hagg's D.H.88 assignment had been to assess the feasibility of the A&AEE prone-pilot testbed concept. was feasible. This too was aimed at the new RAF High Speed Experimental Flight - not because such a design was expected to be especially fast but, rather, to determine the value of prone-pilot positions in future high-speed aircraft. By the time Hagg and his Walton Yacht Works team had turned their attention to the prone-pilot testbed, the HSEF was already losing interest in Hagg's genuinely high-speed proposals. [1] Regardless, Hagg's prone-pilot proposal owed something to the first of those single-engine conversion proposals.

Like the first single-engined concept, Hagg's prone-pilot proposal raised the original D.H.88 wings to a mid-fuselage position. There the similarity ended. Other than this wing repositioning, the Hagg proposal followed the A&AEE's prone-pilot concept quite closely. An obvious difference was that pilot's legs now lay below the wing centre section. The fuel tank above the raised wing was necessarily small. However, this was not seen as a problem as longer flights were not meant to be part of the A&AEE test programme. The Air Ministry accepted this proposal - as the D.H. HSP (for High-Speed Prone). Again, the terminology reflected use by the HSEF rather than an anticipated high speed.

Top Arthur Hagg's D.H.88 prone-pilot conversion as originally proposed, October 1937.

Model-makers at Walton produced a 1/18th scale test article for wind tunnel trials. The 24 foot low-speed wind tunnel at Farnborough produced some unanticipated results. Raising the wings obviously also raised the engines' thrustline. Unfortunately, scaled testing at Farnborough revealed that the resulting propeller wash was likely to create tailplane flutter. The only solution was to redesign the tailplane to raise the D.H.88's stabilizers and elevators up out of this propeller-generated turbulence. Fortunately, this could be accomplished through modifying existing components. Hagg also took the opportunity to refine the tail cone and introduce a tailwheel for better ground handling.

Bottom Revised D.H.88 (HSP) 'Prone Comet' conversion as completed, January 1938.

Actual modifications of Comet K5084 airframe components were completed fairly quickly at Walton. Those components were assembled at RAF Martlesham Heath in late January 1938. With ground checks finished, testpilot Flt Lt H.M. Schofield took the rebuilt 'Prone Comet' into the air early on Thursday, 10 February 1938. [2] In his assessment, Harry Schofield ranked flying characteristics to be as good or better than the standard D.H.88. Visibility during take-off and landing were gauged of "an order of magnitude improvement" over the restricted sightlines from the standard, rear-cockpit Comet. The choice to go with a prone-pilot conversion of K5084 were vindicated.

The rebuilt Comet provided a wealth of test data on prone-position flying. Most of this test work was performed by Sqn Ldr D'Arcy Greig, DFC. [3] It was Greig who was at the controls of K5084 when it experienced an uncontrollable engine fire in flight on 13 June 1938. Greig was forced to take to his parachute over Gedgrave Hall. The burning aircraft came down in the North Sea off of Orford Ness. Settling in over 60 feet of water, no attempt was made to recover the wreckage of the D.H.88 HSP.

__________________________

[1] It was now concluded that service aircraft like the new Hawker Hurricane fighter would be more than adequate to meet the needs of the RAF High Speed Experimental Flight. By the time that either of the single-engined Hagg proposals could be finished, sufficient Hurricane fighters would be available to spare some for HSEF use.

[2] HSEF commander, (T) Wg Cdr Sidney Webster, had convinced RAF Reserve officer and former Schneider Trophy pilot, Flt Lt Schofield, to take on HSEF test pilot duties. Harry Schofield took unpaid leave from his employers, General Aircraft Ltd., to perform this work.

[3] D'Arcy Greig was another veteran of the original High Speed Flight. Now-Sqn Ldr Greig was seconded to the HSEF on leave from his CFI duties at the Central Flying School at RAF Upavon, Wilts.
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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #16 on: July 07, 2021, 07:26:52 AM »
No backstory on this one ... just wanted an excuse to do Robin's mailplane-on-floats concept  ;)
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Offline Robomog

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Re: D.H.88 Comet Follow-Ons
« Reply #17 on: July 07, 2021, 07:44:08 AM »
Inspired !  :-* :-*

Thats  one for the things to do book  :smiley: :smiley: :D

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Offline robunos

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Re: D.H.88 Comet Follow-Ons
« Reply #18 on: July 07, 2021, 11:51:47 PM »
Ooohh !!  Me Likey Lots !!   ;D
Supermarine S.5 floats ? The lower one looks better, though I suppose the extra ventral fin would be more accurate . . .   :smiley:
A further thought, would this need handed engines ? And just to push this even further, combine your Lion powered version with this floatplane, to make a trainer for Schneider Trophy pilots, in a competition that didn't end in 1931 . . .   ;)


cheers,
Robin.
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Offline GTX_Admin

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Re: D.H.88 Comet Follow-Ons
« Reply #19 on: July 08, 2021, 02:52:06 AM »
 :smiley:
All hail the God of Frustration!!!

You can't outrun Death forever.
But you can make the Bastard work for it.

Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #20 on: July 08, 2021, 11:26:35 AM »
Thanks folks. Well-spotted Robin, they are indeed S.5 floats (even kept the floats' racy paint scheme, though not the colour).

Agreed on the ventral fin aesthetics ... but all floatplanes seem to end up sprouting additional tail surfaces. Although, if she'd been given handed engines, maybe not?

I did toy with a single-engined Comet derivative on floats but it looked waaay too Schneider-y. But, I'm pretty sure that there is a racer on its way  ;)
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Offline robunos

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Re: D.H.88 Comet Follow-Ons
« Reply #21 on: July 09, 2021, 05:16:05 AM »
Always did have a thing for the Schneider Racers, specially once I found out Sidney Webster came from my home town . . . though unfortunately the Local Authority don't do anything to celebrate this, doesn't fit their agenda . . .    >:D    :-[


cheers,
Robin.
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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #22 on: July 09, 2021, 07:13:48 AM »
Always did have a thing for the Schneider Racers, specially once I found out Sidney Webster came from my home town . . . though unfortunately the Local Authority don't do anything to celebrate this, doesn't fit their agenda . . .

Hmm, sounds like local enthusiasts need to go around the council. Instead of an appeal to authority/tradition, perhaps more of a 'Local git makes good' approach? Some organization/private entity which would benefit from some publicity would seem an obvious conduit.

A local news search tells me that the Park Place Shopping Centre is closing its entire upper floor and is need of an update. To my eyes their glassed-in, 2-storey escalator alcove needs a plaque and a large-scale model of the S.5 hung from its ceiling   ;D


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Offline robunos

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Re: D.H.88 Comet Follow-Ons
« Reply #23 on: July 10, 2021, 06:19:35 AM »
TBH, I can see Park Place being closed down and 're-developed' . . . If it was up to me, there'd be a statue of Webster on the Bridge, opposite Sister Dora, instead of the useless fountain, or if not there, in front of the Town Hall and Library, with John Carless VC, and the Hippo, and a replica S.5 on the roundabout at the junction of Lichfield Road and Mellish Road, which isn't far from his birthplace in Borneo Street, similar to the E.28/39 replica in Lutterworth. Or even an 'artistic' design like the Spitfire Island in Castle Bromwich, Birmingham . . .


cheers,
Robin.
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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #24 on: July 14, 2021, 10:08:35 AM »
As promised, a racer ... sorta.
_________________________

In 1938, the Admiralty had become interested in an engine in the size-range of the 'R' racing engine. This led to the Rolls-Royce Griffon - an entirely new V-12 which had been influenced by the PV-12 Merlin but was dimensionally similar to the older 'R' types. The Admiralty envisioned the Griffon powering a new generation of 2-seat fighters and strike aircraft.

The Navy was well aware of the RAF's Speed Spitfire (Supermarine Type 323) project, intended for an attempt on the FAI world speed record. That record stood at 379.63 mph established in November 1937 by a modified Messerschmitt fighter - the Bf 109 V.13. But that speed had been exceeded at low level (400 m) by an 'R' powered Supermarine S.6B floatplane racer back in 1931. [1] The Admiralty decided to commission a thinly-disguised record attempt aircraft - the so-called Griffon 'Experimental Engine Demonstration Aircraft'. Since Supermarine was already committed to the Speed Spitfire, the contract for a Naval 'EEDA' went to de Havilland Aircraft.

Known internally as the 'Admiralty Racer', for record-keeping purposes, the DH.108 'EEDA' was referred to as the 'Comet AR'. In reality, the DH.108 had virtually nothing in common with the twin-engined DH.88 Comet racer of half a decade earlier. There were similarities in construction, however. The 'Comet AR' airframe was made almost entirely of wood. This was partly to speed creation but de Havilland was also convinced that the smoothest possible airframe could only be created from rivetless wooden construction. A wooden airframe for a one-off experimental aircraft may also have appeared less suspicious to any prying Air Ministry officials.

The DH.108 was a mid-winged aircraft with the cockpit situated well aft. Those wings were three-spar structures related to the DH.88 wing but with a modern, thicker NACA section and almost 10 feet less span. The fuselage was a moulded plywood form of somewhat complex shape to accommodate the massive radiators needed to cool the large 'Griffon R' powerplant. When retracted, the main wheels of the undercarriage were accommodated in the lower fuselage sides. The tail skid retracted flush to the rear fuselage.

It was intended that current record-holder would pilot the 'Comet AR'. Technically, S/L George Stainforth, AFC, was commanding 802 Naval Air Squadron but any 'experimental' flying would also be done on behalf of the Fleet Air Arm. Accordingly, S/L Stainforth was to be seconded to a new EEDA Flight based at Abbotsinch. As it happened, the speed record was raised by the Germans to more than 469 mph in April 1939. Despite doubts of being able to match that speed, it was decided to proceed with the DH.108. If the new speed record could not be broken, the Royal Navy would simply reveal the DH.108 as its 'Experimental Engine Demonstration Aircraft'. The first flight was planned for early October 1939, but this was not to be ...

_____________________________________

[1] The top speed of the S.6B was 407.5 mph, establishing an Absolute World Speed Record on 29 September 1931
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Offline Robomog

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Re: D.H.88 Comet Follow-Ons
« Reply #25 on: July 14, 2021, 05:26:48 PM »
Just when you think things couldn't get any better you produce this one !

A beautiful bit of streamlined goodness   :-* :-*

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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #26 on: July 15, 2021, 02:29:11 AM »
Cheers Mog! I've got at least one more 'D.H.88 Comet Follow-On' coming. This time, a little bit more realistic  :D
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Offline finsrin

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Re: D.H.88 Comet Follow-Ons
« Reply #27 on: July 15, 2021, 02:46:34 PM »
So many fine variations  :smiley:    Wonder if prone pilot design would be faster  ???     Brian should be here to see the ultra sleek spats.

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Re: D.H.88 Comet Follow-Ons
« Reply #28 on: July 16, 2021, 03:15:37 AM »
Wonder if prone pilot design would be faster

Probably not as the DH.88 was already pretty sleek.

There's an interesting story on the supposed plan to use the DH.88 asa bomber of sorts int he most recent edition of Aeroplane:

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Offline robunos

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Re: D.H.88 Comet Follow-Ons
« Reply #29 on: July 16, 2021, 03:48:05 AM »
As promised, a racer ... sorta.


Ooohh, that looks so good . . . trouble is, someone's going to want to turn it into fighter . . .   ;)       ;D


cheers,
Robin.
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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #30 on: July 16, 2021, 08:26:54 AM »
... Brian should be here to see the ultra sleek spats...

He should ... Brian is very much missed  :(   Those 'semi-retractable speed spats' were my homage to the unforgettable BdB.

... Wonder if prone pilot design would be faster...

As Greg said, probably no faster than the D.H.88 Comet itself. My idea was that the High Speed Experimental Flight would want a prone-pilot trainer in case that avenue was explored for higher-speed service machines - so, ultimately, different prone-pilot service airframes with much more powerful engines.

Ooohh, that looks so good . . . trouble is, someone's going to want to turn it into fighter . . .

Cheers Robin! Mind you, I wouldn't want the job of puzzling through how to fit eight Brownings into that wing  :o
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Offline Robomog

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Re: D.H.88 Comet Follow-Ons
« Reply #31 on: July 16, 2021, 10:38:20 AM »
Bung em in the nose Mosquito style  ???

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Re: D.H.88 Comet Follow-Ons
« Reply #32 on: July 17, 2021, 01:51:28 AM »
The nose was largely fuel:

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Offline Robomog

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Re: D.H.88 Comet Follow-Ons
« Reply #33 on: July 17, 2021, 05:23:40 AM »
Hummm maybe not :-[

Even if you take one tank out the guns will still be pretty close to the other one.

It's one huge flying fuel tank.

Gondolas under the wing Gladiator style ?   But then there will be increased drag

Tricky   :icon_bofh:   ;D

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« Last Edit: July 17, 2021, 05:25:12 AM by Robomog »
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Offline robunos

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Re: D.H.88 Comet Follow-Ons
« Reply #34 on: July 17, 2021, 05:59:01 AM »
Bung em in the nose Mosquito style  ???

Mog
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I was referring to the Griffon engined version . . .   ;)


cheers,
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Offline Robomog

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Re: D.H.88 Comet Follow-Ons
« Reply #35 on: July 17, 2021, 09:07:36 AM »
Yep realised that now  :-[ 

My gondola  suggestion still stands or a fuselage gun pack but  trade off against more drag and limited space,,  it seems everything you come up with means you loose a fuel tank  :-\

This whiffy stuff  makes my brain hurt  :icon_zombie:

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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #36 on: July 17, 2021, 10:57:58 AM »
The nose was largely fuel...

I hadn't realized that there was another, 20 Imp Gal. tank behind the navigator. Cool!

Next installment ...
________________________________________________________________

It is often assumed that the D.H.118 Dragonet was simply a monoplane derivative of the D.H.90 Dragonfly. There were certainly strong family resemblances and D.H.118 did did adopt an unmodified D.H.90 empennage. But, in all other respects, the Dragonet was unrelated to the slightly larger Dragonfly. Indeed, the aircraft with the most in common with the D.H.118 was the D.H.88 Comet racer.

For the D.H.118, Comet wings and nacelles were adopted almost without change. [1] The D.H.118 Dragonet fuselage strongly resembled a shortened Dragonfly unit without the top wing attachment points. However, the interior was quite different - being only a 4-seater. The rear 'bench' seat was really the upholstered top of the main fuel tank (the Comet wings lacking spare for fuel). Somewhat awkwardly, baggage stowage was aft of that tank and accessed through a starboard-side door.

With its thin, monoplane wing and Gipsy Six engines, the D.H.118 Dragonet was a much faster aeroplane than the D.H.90 Dragonfly biplane. Doubtless there would have been a private market for the speedy D.H.118 Dragonet had the War not intervened...

________________________________

[1] There was some local structural strengthening and the cowlings were new - being much more accessible than the older Comet designs.


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Offline GTX_Admin

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Re: D.H.88 Comet Follow-Ons
« Reply #37 on: July 18, 2021, 01:11:19 AM »
Maybe something akin to the Blenheim's belly gun pack:





« Last Edit: July 18, 2021, 01:13:55 AM by GTX_Admin »
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Re: D.H.88 Comet Follow-Ons
« Reply #38 on: July 18, 2021, 08:34:47 AM »
That was what came to my mind but you would have to lose the  rear seat or fuel tank to get it in  ;)

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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #39 on: July 18, 2021, 10:33:50 AM »
Alternatively, underwing gun pods? There's a few contemporary fighters with that arrangement - the Caudron light fighters and Koolhoven F.K.58 come to mind.
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Re: D.H.88 Comet Follow-Ons
« Reply #40 on: July 19, 2021, 01:56:10 AM »
Alternatively, underwing gun pods? There's a few contemporary fighters with that arrangement - the Caudron light fighters and Koolhoven F.K.58 come to mind.


Not sure if the wing would have allowed for though I suppose one might be able to do something akin to those used on the Gloster Gladiator, though even these still needed ammunition to get to them via the wing:



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Re: D.H.88 Comet Follow-Ons
« Reply #41 on: July 19, 2021, 02:58:56 AM »
Not sure if the Blenheim unpacks were fully self contained:

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Offline jcf

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Re: D.H.88 Comet Follow-Ons
« Reply #42 on: July 19, 2021, 03:55:04 AM »
TBH, I can see Park Place being closed down and 're-developed' . . . If it was up to me, there'd be a statue of Webster on the Bridge, opposite Sister Dora, instead of the useless fountain, or if not there, in front of the Town Hall and Library, with John Carless VC, and the Hippo, and a replica S.5 on the roundabout at the junction of Lichfield Road and Mellish Road, which isn't far from his birthplace in Borneo Street, similar to the E.28/39 replica in Lutterworth. Or even an 'artistic' design like the Spitfire Island in Castle Bromwich, Birmingham . . .


cheers,
Robin.

They might be willing to consider some of that if you promise to pay for it.  ;D

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Re: D.H.88 Comet Follow-Ons
« Reply #43 on: July 19, 2021, 04:13:22 AM »
Based on period, why would a Comet fighter even have eight Brownings? It would predate
the requirement.

One thing that would be needed is to swap the position of the cockpit and the center fuel
tank. Reduce the size of the fwd. fuel tank to allow for the ammo tanks and mounts of a
cluster of four Brownings, or perhaps two .303 Browning and two Vickers .50 experimental
aircraft guns.
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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #44 on: July 19, 2021, 10:55:35 AM »
Based on its experiences with the D.H.92 Dragonfly, de Havilland Aircraft made no assumptions about the RAF buying their new D.H.118 Dragonet. [1] Still, it was clear that a potential military market existed for the new design. It was decided to adapt a variant of the Dragonet for the military multi-engine training role. There were already rumours about a forming a new training scheme akin to the 1917-18 Royal Flying Corps Canada (RFC Canada) organization. Orders were already coming in for increasing numbers of D.H.83C Tiger Moth trainers in Canada.

The D.H.118M Dragonet (Military) - as it was named - was to be be a dedicated pilot trainer. In most respects, the airframe was unchanged but the forward fuselage and cockpit areas were completely different. In place of four luxury seats were dual-control positions for a pilot-trainee and an instructor. This cockpit was covered by a new sliding-hood for ease of access (and emergency egress). Behind the side-by-side trainee/instructor positions was a single 'jump seat' positioned above the fuselage fuel tank. [2]

Although designed to British specifications, it was intended that any production military variants would be built by DH's Canadian subsidiary, De Havilland Aircraft of Canada Ltd. The parent company would supply example airframes, some fittings, and other de Havilland subsidiaries would supply powerplants and propellers. These components would be shipped to Downsview for final assembly by 'De Havilland Canada'. It all seemed to make perfect sense. But, the future would reveal that de Havilland Aircraft planners had made two fatal miscalculations.

The lesser of the gaffs involved that rear 'jump seat'. The concept of carrying a training observer was sound - and made the D.H.118(M) more competitive with larger-capacity trainers like the Airspeed Oxford. However, in the D.H.118(M), that observer had little chance of successfully escaping the aircraft in an airborne emergency. In effect, de Havilland had created an oversized baggage compartment in an aircraft which had no need for stowage.

More serious was funding. If an aircraft like the D.H.118M Dragonet (Military) was found to be needed in Canada, who would pay for it? De Havilland brass assumed that superior design was why Canada had chosen the D.H.83C Tiger Moth over a domestic trainer - the Fleet Finch. In fact, the deciding factor for Canada was that D.H.83Cs were paid for by Britain. De Havilland was about to discover that Ottawa would be no more willing to incure costs buying D.H.118(M)s when Britain was willing to foot the bill for Oxfords. There would be no orders forthcoming for the otherwise excellent D.H.118M Dragonet (Military). [3]

________________________________

[1] The travails of working with the Air Ministry on the D.H.93 Don also weighed upon DH head office. Other than elementary trainers, de Havilland had been ignoring most RAF Requirements. The ever-changing demands on the D.H.93 was suggesting that tendering submissions might not be worth the candle.

[2] This 'seat' was more padding on top and forward of the L-shaped fuel tank.

[3] De Havilland got the last laugh. In 1939, 150 Airspeed Oxford were built by DH at Hatfield. In June, 1940, de Havilland bought the remaining shares of Airspeed Limited and Airspeed became a wholly-owned DH subsidiary.
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Offline GTX_Admin

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Re: D.H.88 Comet Follow-Ons
« Reply #45 on: July 20, 2021, 02:09:38 AM »
Based on period, why would a Comet fighter even have eight Brownings? It would predate
the requirement.

One thing that would be needed is to swap the position of the cockpit and the center fuel
tank. Reduce the size of the fwd. fuel tank to allow for the ammo tanks and mounts of a
cluster of four Brownings, or perhaps two .303 Browning and two Vickers .50 experimental
aircraft guns.


I was thinking of something like that or even 1 20mm cannon and a pair of .303s.  One could maybe halve the size of the nose fuel tank to accomodate.
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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #46 on: July 20, 2021, 10:04:36 AM »
I was thinking of something like that or even 1 20mm cannon and a pair of .303s.  One could maybe halve the size of the nose fuel tank to accomodate.

Does it have to be a two-seater? A single-seat evolution would certainly simplify fuel tank placement.

On the 20 mm, its quite a while before the HS.404 is ready (read: reliable enough) for action. Meanwhile the Luftwaffe was using Oerlikon FFs firing 20 x 80RB and the RN had Oerlikon Type S guns with 20 x 110RB.

Three options occur for getting a 20 mm cannon into RAF service in the mid-/late '30s:

- 1) Adopt the Oerlikon FF in the form of the Hispano-Suiza HS.9 (possibly buying now-surplus French tooling);
- 2) Re-barrel Jon's Vickers .5-inch gun to take a 'necked' Vickers 12.7 x 81 round with the Oerlikon shell;
- 3) Enlarge the Vickers .5 inch aircraft gun to be able to accommodate the RN's Oerlikon 20 x 110RB.

Or, a more out-there possibility - develop the bigger Vickers .5 inch Class D (aka HV) for aircraft use (probably by substituting a bunch of aluminum alloy for steel). The 12.7 x 120SR cartridge already packs a punch. But my favorite idea is turning the Vickers HD into an 'Imperial Cannon' - necking the cartridge to 19.1 x 120SR to create a .75-inch aircraft gun  :smiley:
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Re: D.H.88 Comet Follow-Ons
« Reply #47 on: July 21, 2021, 01:54:23 AM »
I like your ideas re the 20mm gun, though the more I think of it, the 12.7mm option is doable too.  I was thinking of this as being about a 1935/36 aircraft and perhaps a long endurance/range fighter - not quite a Zerstörer but maybe something on the path towards.  If one thinks as the Spitfire/Hurricane as short range interceptors this is the long-range bomber escort or perhaps just long endurance standing patrols.  Either might want the second pilot or perhaps the second becomes a radio operator/nav?
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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #48 on: July 22, 2021, 07:33:08 AM »
I like your ideas re the 20mm gun, though the more I think of it, the 12.7mm option is doable too.  I was thinking of this as being about a 1935/36 aircraft and perhaps a long endurance/range fighter - not quite a Zerstörer but maybe something on the path towards.  If one thinks as the Spitfire/Hurricane as short range interceptors this is the long-range bomber escort or perhaps just long endurance standing patrols.  Either might want the second pilot or perhaps the second becomes a radio operator/nav?

Yes, the Vickers .5-inch would be the quickest way to go in 1935-36. On crewing, one possibility would be to have a mix of variants.

For long patrols, navigation could be handled by a 2-seater with .303s only. The rest of the formation would then be single-seaters armed with both .303s and the heavier guns.

For bomber-escort, the 'Big Friends' from Bomber Command could provide the nav. (Although, maybe a 2-seater fighter in the mix to provide for a formation wireless operator?)

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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #49 on: July 22, 2021, 07:39:10 AM »
My take on Comet fighters ...
___________________________

The de Havilland D.H.88F Comet Fighter was considered an interim long-range fighter. Inspired, at least in part, by the German remilitarization of the Rhineland, the RAF's Comet Fighters spent most of their careers on over-water defensive sweeps.

Bottom Show here on armaments trials in early 1938, Comet Fighter AX863 [1] has protective doped patches over the muzzle ports for its .303-inch guns but not its .5-inch Vickers Mk.V ports. This reinforces suggestions that AX863 was employed on trials of experimental explosive rounds (which were technically forbidden by the 1868 Saint Petersburg Declaration). Note that AX863 sports the  'rear light' modification (to improve the pilots aft view).

As its name suggests, the Comet Fighter was a straightforward adaptation of the D.H.88 Comet racer. The reputation of that racer added some prestige to the RAF operating the D.H.88F but the Comet Fighter was effectively a proof-of-concept intended to be replaced by a purpose-made long-range fighter design. That design emerged as the D.H.128 Meteorite. [2]

The D.H.128 was very similar to the D.H.88F in construction but had a slightly longer rear fuselage and reinforced wings. The powerplants were twin de Havilland Gipsy King Series I-DCs. These inverted V-12s were based on the Gipsy Twelve engines Frank Halford was designing for the Albatross airliner. To speed D.H.128 development, Sir Frank abandoned reversed cooling in favour to simpler direct-cooling (hence the 'DC' suffix). [3] The Series I-DC engines also had a higher thrust-line than the reverse-cooled types.

Compared with the D.H.88F, the obvious difference in the D.H.128 design was its forward-placed cockpit. This meant that the armament of four 20mm Oerlikon shell guns could be placed over the aircraft's centre-of-gravity (as could the fuel tanks). Blast-tubes very arranged alongside the cockpit. The view from the forward-positioned cockpit was judged exemplary. Opinion of that cockpit's sliding canopy was much less complimentary. Similar to the hood design which would emerge for the Fox Moth biplane, service pilots found this canopy too small and overly constraining. It was often left open in flight despite being deleterious to this fighter's performance.

Top De Havilland's D.H.128 Meteorite demonstrator. This aircraft was retained at Hatfield by permission of the Air Ministry. The B Class registration E.9. was applied (being inherited from the D.H.84 Dragon prototype when that transport received its civil registration G-ACAN). Upon request, E.9. was delivered to the RAF in early September 1939. This aircraft was lost off of Narvik, Norway on 01 June 1940.

______________________________________________________________________

[1] The RW AX863 was an impressed D.H.84 Dragon I transport.

[2] De Havilland had assigned the name'Dragonstar' to its D.H.124. This name was rejected by the Air Ministry which chose Meteorite as the aircraft's service name.

[3] Shifting to direct-cooling increased drag but reduced both weight and the frontal area of the cowlings. In the initial D.H.88F drawings, reverse-cooling was provided by 'elephant ear' intakes to either side of the nacelle. This also pushed the engines forward, demanding an even longer extension to the rear fuselage and more greatly enlarged tail surfaces. All this could be scaled back by adopting direct-cooling.
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Offline Old Wombat

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Re: D.H.88 Comet Follow-Ons
« Reply #50 on: July 22, 2021, 03:31:26 PM »
 :smiley:
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Offline Robomog

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Re: D.H.88 Comet Follow-Ons
« Reply #51 on: July 22, 2021, 06:27:50 PM »
This thread just keeps on giving !

Love the DH 88F   :-*

(Hmmmm  thinks: DH88f on floats ?)


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Offline jcf

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Re: D.H.88 Comet Follow-Ons
« Reply #52 on: July 23, 2021, 01:28:51 AM »
 :smiley:
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Sense doesn’t come into it. People are
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Re: D.H.88 Comet Follow-Ons
« Reply #53 on: July 24, 2021, 02:33:09 AM »
 :smiley:
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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #54 on: July 24, 2021, 07:22:07 AM »
Thanks folks!

...(Hmmmm  thinks: DH88f on floats ?)...

I know, right? What is it about the Comet that keeps suggesting floats? But it sure does ...  ;D
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Offline ChernayaAkula

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Re: D.H.88 Comet Follow-Ons
« Reply #55 on: July 29, 2021, 08:53:18 AM »
The D.H.128 Meteorite is just lovely!  :-*
Cheers,
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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #56 on: July 30, 2021, 07:17:07 AM »
Thanks Moritz! I really do wonder how the Gipsy Twelve would have faired had DH offered a variant without reversed-cooling.

Such an engine would have been in the same class as the Renault 12R, Walter Sagitta I-MR, or Isotta Fraschini Gamma. None of those engines excelled as fighter powerplants. But I can imagine the imaginary conventionally-cooled Gipsy Twelves on up-powered Oxfords, for example ...
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Re: D.H.88 Comet Follow-Ons
« Reply #57 on: July 31, 2021, 06:40:03 AM »
Thanks Moritz! I really do wonder how the Gipsy Twelve would have faired had DH offered a variant without reversed-cooling.

Such an engine would have been in the same class as the Renault 12R, Walter Sagitta I-MR, or Isotta Fraschini Gamma. None of those engines excelled as fighter powerplants. But I can imagine the imaginary conventionally-cooled Gipsy Twelves on up-powered Oxfords, for example ...

There was nothing in the design of the Gipsy King/XII that required reverse-flow cooling, that
was a matter of the installation design which resulted from De Havilland's desire to minimize
drag.

The main thing that worked against the engine was size and weight, larger than a Kestrel V in all
dimensions, weighed 100lbs more and produced 250+/- fewer horsepower. Truthfully the engine
had a pathetic output for its size with a power to weight ratio of a paltry 0.4 hp/lb.
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Re: D.H.88 Comet Follow-Ons
« Reply #58 on: July 31, 2021, 11:12:01 AM »
Sound like DH would have better focusing on reducing weight rather than drag. Although I had fun using the Gipsy Twelve for my whif, none of those air-cooled IV-12s made for much of a combat engine - even the more powerful Isotta Fraschini Delta or Ranger V-770.
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Re: D.H.88 Comet Follow-Ons
« Reply #59 on: August 01, 2021, 02:05:51 AM »
Sound like DH would have better focusing on reducing weight rather than drag. Although I had fun using the Gipsy Twelve for my whif, none of those air-cooled IV-12s made for much of a combat engine - even the more powerful Isotta Fraschini Delta or Ranger V-770.

Even if they had reduced the weight of the engine, you'd still want minimum drag for
the airframe design. Even if they'd had a reduced weight version, De Havilland would
have still used the same design for the nacelles of the Albatross and the cowling of the
Don.

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Re: D.H.88 Comet Follow-Ons
« Reply #60 on: August 01, 2021, 02:40:37 AM »
What about a version with tricycle landing gear and the engines reversed into a pusher arrangement?
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Offline apophenia

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Re: D.H.88 Comet Follow-Ons
« Reply #61 on: August 01, 2021, 04:39:32 AM »
Even if they had reduced the weight of the engine, you'd still want minimum drag for the airframe design. Even if they'd had a reduced weight version, De Havilland would have still used the same design for the nacelles of the Albatross and the cowling of the Don.

True. I'd been focusing in on other, more conventional air-cooled IV-12 approaches. Perhaps DH realized that this market was already glutted. So it was either come up with a fresh arrangement with low-drag advantages or just stick with the existing straight inline Gipsy families?

What about a version with tricycle landing gear and the engines reversed into a pusher arrangement?

I like that! And it would certainly change the look  :smiley:
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Re: D.H.88 Comet Follow-Ons
« Reply #62 on: August 01, 2021, 10:03:38 AM »
Reverse flow concepts for air-cooled engines were on other peoples minds because the inherent problem
with an inline air-cooled engine is that the rear cylinders are the ones that tend to overheat first, also it
had some promise in cleaner airframe design. But again this a matter of airframe and installation design
rather than engine design, and the best results were when the airframe company worked closely with the
engine manufacturer. Douglas's humongous oversized cowlings on the C-74 for the R-4360 drove the P & W
folks up the wall, Andrew Wilgoos acerbically wondering if Douglas intended to use the extra space for a
luggage compartment.
 ;D

If there had been a commercial, or military, interest in their IV-12 engine DH would have sold it to whoever
wanted one and not worried much about how they wanted to use it. The existing I-6 engines wouldn't have
been powerful enough for the Albatross, and again they were larger and heavier than the I-6 engines from
the competition and had a lower horsepower to weight ratio. DH's engine side in the '30s definitely showed
the effect of not having a good replacement for Frank Halford.

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Re: D.H.88 Comet Follow-Ons
« Reply #63 on: August 05, 2021, 10:45:45 AM »
What about a version with tricycle landing gear and the engines reversed into a pusher arrangement?

I had a go at trike-geared pushers but none of them worked visually. So, I've shifted gears and returned to Arthur Hagg at Walton-on-Thames ...

High in the Sky - a Comet-Influenced Photo-Recce Aircraft

With the rejection of their 'High-Speed Hagg' concepts, the Walton Yacht Works team had returned to small craft design. However, as war-clouds darkened, the Air Ministry made inquiries about the development of a dedicated high-speed photo-reconnaissance aircraft derived from the basic de Havilland D.H.88 structural techniques. Like the second of the 'High-Speed Hagg' concepts, this was to be a single-engined aircraft. The actual design would be constrained by the Air Ministry's required use of existing, in-service components - specifically the engine installation and main undercarriage from the Supermarine Spitfire fighter.

The requirement for a Spitfire landing gear dictated a low-set wing but also presented a major design challenge - since there was no way that such an undercarriage could be accommodated by the very thin profile of the D.H.88 Comet wing. While many of the original construction techniques of that Comet wing were kept, Hagg completely revised his actual wing design for the new 'Recce Comet'. The birch-ply and spruce rib concept was retained and so too was the RAF 34 airfoil. However, that airfoil section was deepened to increase the thickness/chord ratio. The latter to allow stowage space for a retracted main undercarriage within these thicker wings. The presence of that landing gear dictated changes to the D.H.88's triple-spar arrangement.

For what became the Walton-designed de Havilland D.H.188W, a beefier arrangement of two full-span spars was adopted - these spars being positioned at about 20% and 65% chord. A third stub-spar - positioned at 40% chord - supported and absorbed the loads of the main undercarriage legs. Outboard of that stub-spar, stiffness was ensured by spruce stringers. The Comet wing had been skinned with a combination of spruce planking (inboard) and birch veneers (outboard) attached to the ribs and stringers. For the D.H.188W, Hagg adopted a new technique whereby the entire wing skin was formed by pre-moulded plywood panels - in upper, lower, and leading edge sections. The entire structure was then covered with a filling compound - to smooth over joints and wood grains - before painting.

Hagg's High-Flyer - the de Havilland D.H.188W Danby

By an agreement arranged through the Air Ministry, prototype airframe components would be prepared at Walton Bridge and shipped the 40 miles to Hatfield Aerodrome in Hertfordshire for completion by DH. As assembled, the prototype D.H.188W was powered by a standard Spitfire Mk.I engine. But, in place of the Spitfire's two-bladed Watts propeller, the D.H.188W's 1,030 hp Merlin I drove a 3-bladed de Havilland two-pitch metal propeller. The main undercarriage was unchanged from the Spitfire but a fully-retractable tail skid was employed. For its photo-recce role, the prototype D.H.188W was fitted with two, government-supplied F.24 5-inch cameras in its rear fuselage. This camera type was an odd choice since the new aircraft was best-suited to a high-altitude role.

Bottom Prototype D.H.188W Danby still showing its de Havilland Class B registration E.15. (despite the application of RAF Type A roundels). Note the pointed spinner for the two-pitch DH prop and retractable tail skid.

Despite having provided the photographic equipment, the Air Ministry insisted that a vertically-placed F.24 camera with an 8-inch lens be installed. The tail skid was also a source of complaint. Although a drag penalty invariably resulted, a fixed Spitfire tail wheel was substituted for the skid. Other minor changes were also made - eg: to improved heating ducts both to the camera bay and for windscreen demisting. A slight tail-heaviness was addressed but switching from the two-pitch propeller to a slightly heavier constant-speed DH prop. All of these changes were quickly introduced on production D.H.188W airframes then being prepared at Walton Bridge. When completed at Hatfield, these production D.H.188Ws were delivered to Sidney Cotton's newe PR Unit at Heston with the name Danby Mk.I assigned. [1]

Top Production de Havilland D.H.188W Danby finished in the RAF's new 'Camotint' finish. Note the change to ID Blue (from Roundel Blue) on the fuselage Type A roundel and complete elimination of underwing roundels.

The first operational flight by an RAF D.H.188W Danby took place on 06 September 1939 when the PR Unit's Shorty Longbottom overflew the neutral Dutch port of Ijmuiden. The first truly long-range mission followed on 29 September when the German island of Sylt was photographed from almost 32,000 feet. Unfortunately, in the absense of cabin pressurization, higher flights were not practical. As a result, the longspan wings of the Danby were not fully taken advantage of. [2] By October 1939, two loaned Spitfires had been 'Cottonized' at Heston and were ready for action. By comparison, the Danby Mk.I had a slight altitude advantage and greater range but the gunless Spitfire PR Type A was faster.

With PR Spitfire range improving, in early 1940, the new Ministry of Aircraft Production chose to eliminate D.H.188W Danby production. Counter-arguments that the Danby used fewer 'strategic' materials in its construction could not outweight MAP's desire to eliminate duplication by reducing the number of aircraft types in  production. With never more than a half dozen Danbys in service at any time, the D.H.188W quickly became a half-forgotten aviation history footnote.

________________________________________

[1] The name Danby honoured World War I Royal Flying Corps aerial photographer, Major C.S. Danby.

[2] The D.H.188W Danby had a wing span of 44 feet with an area of 212.5 sq ft. By comparison, the Spitfire PR Type A had a wing span of 36 feet 10 inches and an area of 242 sq ft.
« Last Edit: August 06, 2021, 04:11:01 AM by apophenia »
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