Learjet

[Jeffry Fontaine]

A place to discuss all things related to all models of the Learjet in civil and military aviation roles. 

Links:

Click on html to visit to Bombardier Learjet corporate web page.

Click on html or thumbnail to go to Wikipedia - Learjet


Click on html or thumbnail to go to Wikipedia - C-21 Learjet/Learjet 35/36



Google search results for "Learjet"


Further research shows that there are "aftermarket" modifications available for the Learjet:

Avcon offers a modification kit for a set of ventral fins to improve directional stability. 

Raisbeck offers a wing modification kit and a ventral cargo pod. 

[Jeffry Fontaine]

Anyone have a decent image or three of the stores pylon that is located under each wing that can be shared here to this forum or a link to such information.

TIA

[perttime]

A couple of pylons on Finnish Learjets are somehow visible in this set on Flickr:
http://www.flickr.com/photos/saminkuvat/sets/72157627316191242/detail/

This gallery shows, among other things target tug gear on Learjets:
http://pekkapura.kuvat.fi/kuvat/Lentokoneet/Sotilaskoneet/

Example:


http://pekkapura.kuvat.fi/kuvat/Lentokoneet/Sotilaskoneet/Learjet%2035_21052010-6.jpg/_full.jpg

[Jeffry Fontaine]

Thanks for sharing those links.  Great images of the aircraft but nothing up as close as I would prefer for the pylons.  Also looks to be more than one type of pylon so that complicates things too. 

[raafif]

are those fishing nets ?  Oz coast-guard could do with a few of them aircraft for the shark season 

[elmayerle]

They are targets.  The hasegawa limited run US-36 Learjet has pylons with stores as well as enlarged forward tiptanks for sensor fits.  It's tempting to combine that with the Finnish ESM fit.  Note, this kit also has the underfuselage radome seen here.  Another common mod for the Learjet is a one or two camera installation fitted roughly where the Finnish aircraft have that radome.

[Jeffry Fontaine]

Having the right description resulted in a link to one of the on-line hobby shops in Japan that provides images of the kit contents and instruction sheet.  The attached image is extracted from the instruction sheet image and enlarged to show the profile of the left and right stores pylons used with the military version of the Learjet 35/36. 

[elmayerle]

Glad to help.  Once upon a time I was an engineer at Learjet (granted, this was over 30 yeras ago, but I still remember a number of details) and took part in the certification, both US and Foreign, of the Model 55.

[kitnut617]

Is there a 1/72 kit of this Learjet ?

EDIT: (much later)  I've answered my own question, yes, loads of manufacturers made a 1/72 kit of this aircraft, RVHP did a whole bunch of them including the Finnish Air Force one.  Now all I need to do is find one   

[Jeffry Fontaine]

Search results from Google show two kits in two different modeling mediums:

Resin: RVHP 72207 Learjet

Vacuum-Formed: Rareplanes Learjet

[kitnut617]

My first look through my PAK-20 book didn't come up with anything Jeff, but then I found I should have been looking under 'Gates' Learjet.

Seems there was a 1/72 kit done by Aeropoxy, Aurora, Microwest, your mentioned Rareplane and RVHP and Top Gun.

[Diamondback]

How 'bout a COIN Learjet? Stick a gun-pod on the belly and some MER's on those wing pylons, maybe add a Sidewinder rail near the wingtip. Have all the externals removable to be stowed inside and you're just another bizjet when the job's done.

[elmayerle]

How 'bout a COIN Learjet? Stick a gun-pod on the belly and some MER's on those wing pylons, maybe add a Sidewinder rail near the wingtip. Have all the externals removable to be stowed inside and you're just another bizjet when the job's done.

Got something like that in mind for a covert operation, though I might use MB-326-style gun pods on the inboard hardpoints that are normally the only ones used (be a rather modified wing to add strength - undoing some design changes GLC did to save production cost and which didn't hurt eh strentgh of the civilian wing - essentially going back to the original P-16 wing structure0.  that would give me three hardpoints on each side.

Note, there have been some GLC proposals using these potential hardpoints; much like the Model 24 test aircraft that flew with "Longhorn" wings also flew with an experimental underwing tank installation on the inner-most hardpoints.

[Jeffry Fontaine]

How about a modification to the fuselage to incorporate a small door in the underside of the aircraft to allow cargo to be dropped?  Something similar was done with two Douglas A-26 Invaders that were modified for covert supply drops and operated by the CIA.  A clam-shell type door or better yet, a drop down ramp style door so that cargo could be delivered by air drop.

[elmayerle]

Not the easiest trick in the book.  Best bet would be a large fairing on the opposite side of the fuselage from the main door.  Disguise it as a large camera fairing for airborne photometry but have the camera removable for dropping cargo.  Part of the problem is that there's very little of the small Learjet fuselage that's constant-section, making large doors somewhat difficult.  You might could do something with a Model 55 or derivative thereof, but those are definitely more noticeable.

[Jeffry Fontaine]

Not the easiest trick in the book.  Best bet would be a large fairing on the opposite side of the fuselage from the main door.  Disguise it as a large camera fairing for airborne photometry but have the camera removable for dropping cargo.  Part of the problem is that there's very little of the small Learjet fuselage that's constant-section, making large doors somewhat difficult.  You might could do something with a Model 55 or derivative thereof, but those are definitely more noticeable.

A rear hatch/door/ramp located under the fuselage behind the wing and below the engines would alleviate the issue of obstructing the engines or turning your drop loads into FOD.  That is the only way I see around it.  As long as the door is not of any significant size the issue of structure should not be impossible to over come.  Examples of what I am trying to convey are pretty much every aircraft that has a rear ramp or ramp plus clam-shell doors.  The size of the door/ramp would be small so as to not become a liability to the airframe integrity and not something that would be for dropping personnel, just small bundles of cargo with parachutes.  The kind of thing that could support agents or operatives in the field where a larger aircraft would jeopardize the mission or operation.  So think of an access door that is about two feet wide and three to four feet in length as approximate size. 

[perttime]

I wonder what kind of structure there is in that area on a Learjet. Cutaway drawings show lots of what looks like fuselage frames, on the top side, near the engines.

[Jeffry Fontaine]

Making the door not part of the pressurized compartment would problem reduce a lot of the problems concerning the strength of the structure.  The pressure bulkhead that makes up the rear of the passenger compartment could have a door installed that could then be opened and the outside door opened to enable air drop operations.  Looking at aircraft such as the C-141 and C-5 with the large clam-shell doors that cover the actual loading ramp this would be nothing as extravagant as that.  More like the doors or crew access hatches you would find on the bottom of aircraft like the B-25 Mitchel for example.  Having it open down into the airstream would be practical to assist in getting the load clear of the aircraft to deploy the parachute.  The underside of the Learjet in that area is quite free of obstructions as it is so it would be ideal.  From an operational security perspective the Learjet would not appear to be a standard cargo carrying aircraft so compromise prior to reaching the drop zone would be reduced to just before or immediately after the cargo has been discharged.  Again, at low level and relatively high speed the mission would be complete and the aircraft on an egress heading before the parachuted load had hit the ground. 

Maybe a good designation for this version would be MC-21. 

What would be an appropriate program name for this aircraft?  A Program name beginning with "Combat" or "Pave" would seem appropriate.  Examples of such can be seen with the various C-130 project/mission code names such as Combat Talon or Pave Pronto.  Maybe Combat Black or Pave Jack as a play on "C-21" and the card game of Black Jack? 

[elmayerle]

The problem is that the path from the pressure bulkhead to the area under and between the engines takes you right through the main fuel bladder cells for the aircraft.  Redesigning the fuel system around such a passage would very likely result in a radical reduction in range.  If you're going to put anything in, it would almost have to be forward of the wing.  It's doable, but a definite engineering challenge.

[Jeffry Fontaine]

The problem is that the path from the pressure bulkhead to the area under and between the engines takes you right through the main fuel bladder cells for the aircraft.  Redesigning the fuel system around such a passage would very likely result in a radical reduction in range.  If you're going to put anything in, it would almost have to be forward of the wing.  It's doable, but a definite engineering challenge.

Which is why I wanted to find an image of the wing stores pylons so I could add on a pair of fuel tanks to make up for the loss of fuel in that area.  :)

[elmayerle]

The problem is that the path from the pressure bulkhead to the area under and between the engines takes you right through the main fuel bladder cells for the aircraft.  Redesigning the fuel system around such a passage would very likely result in a radical reduction in range.  If you're going to put anything in, it would almost have to be forward of the wing.  It's doable, but a definite engineering challenge.

Which is why I wanted to find an image of the wing stores pylons so I could add on a pair of fuel tanks to make up for the loss of fuel in that area.  :)

if memory serves me correctly, 24-218 flew with the Longhonr wing and underwing tanks.   Or at least such a configuration was schemed.  Though, really, the center of the three hardpoints carried by the P16 would work better by giving better clearance with the runway.

[Jeffry Fontaine]

Evan, I can appreciate your argument against such a modification but when I discovered that something like this had actually been done with the Douglas B-26 Invader for the CIA I thought it would be interesting to see something similar done with the rather innocent looking Learjet.  Granted the other modifications to those B-26 airframes were extensive including a completely redesigned cockpit and an actual terrain following radar suite in the nose.  The poor loadmaster was stuck in the back with no way out unless he went out the newly installed cargo door and the flight crew were in a similar situation up front in needing to crawl out of the cockpit to that same door in the back to egress the aircraft.  Not a very well thought out design to be honest.  At least with the Learjet you have a normal access door right up front so all that is needed is a means to eject cargo from the aircraft that does not threaten the engines or airframe.  The ideal location for that is as far back as you can get there under the engines and behind the wings. 

[elmayerle]

For getting out of the cockpit quickly, you want the escape hatches certified as part of a mod. for package carrying that filled the fuselage aft of the cockpit bulkhead.  Given the engine locations, if you go out the underside just before the wing, you should clear everything (the engine intkets being over the wing or close enough that you won't get swept up).  Still, I could see a "tunnel" to such a below the engines drop hatch that would leave most of the fuselage tanking intact; it wouldn't be spacious, but it could work.  I suspect you might need rollers on the floor to slide down it.

[Daryl J.]

The Lear 35.  As a boy it was my dream to own one.  Why?  I loved to travel and getting places fast seemed best in  Lear jet. 

[elmayerle]

The Lear 35.  As a boy it was my dream to own one.  Why?  I loved to travel and getting places fast seemed best in  Lear jet.

Only got a chance to fly in 55-002, but 'twas a most enjoyable way to fly.

[raafif]

The next version ?



by DreamsOfMachineArt.

[GTX_Admin]

Cool.  AI Generated I presume?

[raafif]

Cool.  AI Generated I presume?

Yes, one of the few AI pics that don't distort & does make sense.

[elmayerle]

How about a modification to the fuselage to incorporate a small door in the underside of the aircraft to allow cargo to be dropped?  Something similar was done with two Douglas A-26 Invaders that were modified for covert supply drops and operated by the CIA.  A clam-shell type door or better yet, a drop down ramp style door so that cargo could be delivered by air drop.

I reviewed my memories and, if you are willing to depressurize for the drop, drop hatch installations do exist, generally opposite the main door at the front of the fuselage.

[elmayerle]

An idea for a Learjet 35/36XR incorporating the inboard wing glove tank of the Lear 25G conversion and a similar thickening of the engine pylons to reduce interference drag.  And then an extended range version of that with underwing tanks, possibly with pylons again designed to reduce interference drag.

[Jeffry Fontaine]

Why not go with a pair of "slipper tanks" (an example of which can be found in the old Hawk Models/Testors//Italeri U-2C kit) in lieu of pylons under wing and attached fuel tank?

[elmayerle]

Why not go with a pair of "slipper tanks" (an example of which can be found in the old Hawk Models/Testors//Italeri U-2C kit) in lieu of pylons under wing and attached fuel tank?

Possibly.  I was looking at what could be done with the existing tip tanks in a new location.  Perhaps a very short pylon with a fairing so that the tank appears as a slipper tank, though you might have clearance problems with the flaps that way.

[raafif]

over-wing tanks like the Lightning ?