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rmoore7734
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LearJet 35/36 engine upgrade (higher thrust engine)

Tue Dec 11, 2018 5:57 pm

Saw this article just below and sounds like the Honeywell TFE731-3c (dash 3C engine ? ) with 3700 pounds of thrust replacing the original TFE731-2 rated at 3500 pounds of thrust.

https://nashvilleaircraftmanagement.com ... ighter-jet

Looked on google to see where there are other references to this but only found that article.

Maybe not too much of a conversion problem being the "Max Envelope Diameter" and the length are the same on both engines ?
https://aerospace.honeywell.com/en/prod ... fan-engine.

Along with the ZR-lite Bat Wing modification as suggested in the article must be a helluva rocket ship more so.
Wonder what company is doing those conversions ?
 
747Whale
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Tue Dec 11, 2018 6:20 pm

The Lear 35/36 never struck me as much of a "rocket ship." The Lear 20 series definitely got up and went; but they also burned fuel like it was never there, enough so that the fuel gauge visibly moves.

I don't think an extra 200 lbs of thrust a side would be that significant.

The Raisebeck mod ("ZR-lite" or "bat wing") is designed to allow a bit more efficiency, but won't make the airplane perform like a rocket ship. It promises a .02 M1 cruise increase...not really rocket-like.

The Lear 35's are long in the tooth, with acquisition costs low; upgrading engines and adding airframe mods can quickly exceed the cost of the airplane.
 
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rmoore7734
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Tue Dec 11, 2018 6:48 pm

747Whale wrote:
The Lear 35/36 never struck me as much of a "rocket ship." The Lear 20 series definitely got up and went; but they also burned fuel like it was never there, enough so that the fuel gauge visibly moves.

I don't think an extra 200 lbs of thrust a side would be that significant.

The Raisebeck mod ("ZR-lite" or "bat wing") is designed to allow a bit more efficiency, but won't make the airplane perform like a rocket ship. It promises a .02 M1 cruise increase...not really rocket-like.

The Lear 35's are long in the tooth, with acquisition costs low; upgrading engines and adding airframe mods can quickly exceed the cost of the airplane.


Yes mods like this with glass cockpit upgrade. Costs $2 million and six months of downtime
https://www.bjtonline.com/business-jet- ... ized-lj-35
 
GalaxyFlyer
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Wed Dec 12, 2018 1:10 am

I don’t know about the 35s, but adding 350 pounds per side created a large increase in the Lear 75’s Vmcg having real knock-on effects to wet and lightweight runway performance.

GF
 
Max Q
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Wed Dec 12, 2018 2:30 am

Looks good and impressive climb performance but all the Learjets are still slow, cruising at what .78 Mach ? especially by today’s standards with several types capable of .85 to .90 Mach
The best contribution to safety is a competent Pilot.


GGg
 
747Whale
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Wed Dec 12, 2018 8:09 am

Depends on which Lear; .81 M1 up to .86 M1.

None of those other aircraft are going to come into the Lear's performance range for the same price point, especially in today's market.
 
Max Q
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Wed Dec 12, 2018 11:22 am

747Whale wrote:
Depends on which Lear; .81 M1 up to .86 M1.

None of those other aircraft are going to come into the Lear's performance range for the same price point, especially in today's market.




I’d be interested to see the Learjet that can
do .86 Mach with that old technology, barely swept wing, the 75 series, their ‘latest and greatest’ has an MMO of .81


Which model is that then ?


I believe you are mistaken
The best contribution to safety is a competent Pilot.


GGg
 
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rmoore7734
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Wed Dec 12, 2018 3:10 pm

Correction: I said 3700 pounds of thrust but with so many variations of the dash 3 TFE731 it could be 3650 pounds of thrust. Not enough info in article to say which one.
 
747Whale
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Wed Dec 12, 2018 4:40 pm

Max Q wrote:
I’d be interested to see the Learjet that can
do .86 Mach with that old technology, barely swept wing, the 75 series, their ‘latest and greatest’ has an MMO of .81


I primarily flew the Lear 24, 25, 35, and 36, in charter, ambulance, government work, and special assignments with hardpoints, stores, etc.

Mmo and numerous limitations vary somewhat with a large litany of wing features. I have flown all the wing types, from the "hard" wing to the Century w/softflight, XR, etc. As a general rule, the 20 series Lears are .82 M1, and the Lear 35/36 .81 M1. (the Lear 31 is also .81 M1).

http://mrmoo.net/pilot/LR25/LR25%20Cock ... ndbook.pdf

The 20 series Lears will easily go through Mmo with available thrust; the 30 series are more gentlemanly and benign. They still perform well. the 20 series are rocketships and they do perform. The 35 series not as much.

.86 M1 is incorrect; the correct number for the 20 series is .82 M1, which the aircraft do with no trouble at all. Enough so that many operators would deactivate the overspeed warning and fly it faster.

I have been past .86 in the learjet, without ill effect.

Which Lears do/did you fly?
 
nws2002
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Wed Dec 12, 2018 5:07 pm

We had a Lear 36 with -3 engines done via STC. It did perform slightly better, when it worked, but we had a lot of issues getting everything to work with the DEECS. I know the engine gauges had to be replaced and they modified some parts on the engine mount/pylon. Once the engine lease was up, it made more sense to remove the -3 engines and go to -2C engines instead, which meant swapping gauges again and changing out the parts that were modified.

With these older aircraft, the engine maintenance plan rate through Honeywell MSP is pretty much the same as the lease rate on engines. So for us it generally makes more sense to purchase the aircraft, sell the existing engines, and then lease engines. Consistent hourly rate without the worry about unforseen engine maintenance costs.
 
Max Q
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Wed Dec 12, 2018 10:42 pm

747Whale wrote:
Max Q wrote:
I’d be interested to see the Learjet that can
do .86 Mach with that old technology, barely swept wing, the 75 series, their ‘latest and greatest’ has an MMO of .81


I primarily flew the Lear 24, 25, 35, and 36, in charter, ambulance, government work, and special assignments with hardpoints, stores, etc.

Mmo and numerous limitations vary somewhat with a large litany of wing features. I have flown all the wing types, from the "hard" wing to the Century w/softflight, XR, etc. As a general rule, the 20 series Lears are .82 M1, and the Lear 35/36 .81 M1. (the Lear 31 is also .81 M1).

http://mrmoo.net/pilot/LR25/LR25%20Cock ... ndbook.pdf

The 20 series Lears will easily go through Mmo with available thrust; the 30 series are more gentlemanly and benign. They still perform well. the 20 series are rocketships and they do perform. The 35 series not as much.

.86 M1 is incorrect; the correct number for the 20 series is .82 M1, which the aircraft do with no trouble at all. Enough so that many operators would deactivate the overspeed warning and fly it faster.

I have been past .86 in the learjet, without ill effect.

Which Lears do/did you fly?





I’ve not operated any jets that small, the first jet aircraft I flew was the 727 which which had a highly swept wing giving it excellent high speed performance


Unlike the Learjet, .86 seemed like a big exaggeration of its capabilities with that almost straight wing and you corrected yourself on that


There were a few pilots that got themselves into real trouble by disabling overspeed warnings in the Lear and intentionally exceeding Mach limitations



Not being a test pilot it’s not something I would consider
The best contribution to safety is a competent Pilot.


GGg
 
747Whale
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Wed Dec 12, 2018 11:48 pm

There's a lot of mythology about the Lear and its high speed characteristics, all untrue. I've heard wild tales about aileron buzz, and controls slamming side to side, severe mach tuck, all kinds of lore. I was in Martha's Vinyard one day and ran into a lear pilot who expounded at great length about what happens if one exceeds Mmo in the airplane. He described a sever mach tuck tendency, violent pitch instability, and ailerons that snapped the control yoke left and right. I asked him how he knew this.

He told me he'd seen it in the simulator, and he'd been told it at Flight Safety or Simuflite. I asked if he'd ever read any of Pete Reynold's writing about his time in the test and development of the Lear, and was told no. Too bad, because Pete published an entire paper describing the benign flight characteristics of the Lear series at Mmo and beyond, and specifically detailed the mild aileron buzz that might be experienced on some wings (Lears have had a number of wing mods), and the fact that mach tuck in the airplane was little more than a lessening of stick force in the transition. No significant tuck.

I don't think there's a single 20 series Lear pilot that hasn't had excursions well past Mmo. The airplane will get there very quickly, and if cruising close to Mmo (which is common in those airplanes), even a bit of turbulence will get it there. Add to it the less than stellar autopilots in those airplanes and it's not hard to wind up in that region...a non-event.

Pete detailed in his paper the fact that the simulator actions were extreme exaggerations programmed to illustrate a point, but that they did not represent what could be expected from the airplane.

The Lear wing is swept; it's got fairly straight trailing edge, depending on the wing and mod.

The B727 has a 32 degree wing sweep, about the same as any other transport category airplane, and cruises typically in the same range.

The Lear 35 has the same Mmo as the 737.
 
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tb727
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Thu Dec 13, 2018 12:32 am

The only thing that would improve a Learjet would be to chop it up.
Too lazy to work, too scared to steal!
 
747Whale
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Thu Dec 13, 2018 12:21 pm

I've got a lot of respect for the thought and design that Bill Lear put into the Learjet. I spent several years in them, including research flying them in thunderstorm penetrations.

They're good, well designed airplanes. They've become a bit dated, and the cockpits tend to be a bit tight, but they're well built, and well designed. Improvements over old navigation capabilities, structural enhancements (Raisbeck locker and ventral fins, for example) are definite improvements, and there have been offerings to replace the engines on 20 series to make them more compliant. I've flown Lears into some fairly extreme environments, and have respect for the airplane, both what it can and can't do.

It would be a shame to chop one up.
 
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tb727
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Thu Dec 13, 2018 7:50 pm

I've done all that too in them but I have some opinions that differ from yours lol. The thunderstorm stuff wasn't research, but rather lack of good radar and/or poor choices in my youth. Never want to do that again.

I will say I'd love to take a 24 around the patch again. They could get you into and out of trouble pretty quick.
Too lazy to work, too scared to steal!
 
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rjsampson
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Thu Dec 13, 2018 8:03 pm

747Whale wrote:
I've got a lot of respect for the thought and design that Bill Lear put into the Learjet. I spent several years in them, including research flying them in thunderstorm penetrations.


Having not flown a Learjet, I'm not qualified to comment on much, lest thunderstorm penetration.

But oh boy, the comment on Bill Lear's thought and design being positive will be hotly refuted by many on this forum with experience, inside and out.

Do a Google search for "Learjet Nightmares" and you'll immediately get a link to that thread.
"..your eyes will be forever turned skyward, for there.." yeah we know the DaVinci quote. Unfortunately, we're grounded :(
 
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tb727
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Fri Dec 14, 2018 12:58 am

Oh no, I don't think he's gonna like that thread. I'm apologizing ahead of time.
Too lazy to work, too scared to steal!
 
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rjsampson
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Fri Dec 14, 2018 2:03 am

tb727 wrote:
Oh no, I don't think he's gonna like that thread. I'm apologizing ahead of time.


Yeah, he probably won't like that thread at all: viewtopic.php?t=774999

Well over 100 responses, and I think I counted over 25 people with direct Learjet 2x/3x experience, none of them positive. Apparently, A&Ps assigned to the aircraft put their health at hazard, lest they fall into alcoholism. :drunk:
"..your eyes will be forever turned skyward, for there.." yeah we know the DaVinci quote. Unfortunately, we're grounded :(
 
kabq737
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Fri Dec 14, 2018 2:43 am

tb727 wrote:
Oh no, I don't think he's gonna like that thread. I'm apologizing ahead of time.

The writing in that thread is so great and entertaining that it has become one of my favorite A.net threads of all time regardless of subject matter!
Been on: 320, 321, 333, 733, 73G, 738, 739, 744, 752, 763, 764, 772, 789, C208, CR7, CR9, BE20, MD83, MD88, MD90, E70, E75, E90, TRIM
Flown: SEEKER, C150M C172N, C172R, C172S, C182RG, DA40, PA-46
 
747Whale
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Fri Dec 14, 2018 5:45 am

tb727 wrote:
I've done all that too in them but I have some opinions that differ from yours lol. The thunderstorm stuff wasn't research, but rather lack of good radar and/or poor choices in my youth. Never want to do that again.

I will say I'd love to take a 24 around the patch again. They could get you into and out of trouble pretty quick.


Mine was a bit different. With two hardpoints and packages beneath each wing, pyrotechnics, cameras, sensors, and a host of other packages and gear sticking off the outside of the airplane, we build dedicated radar stations, and went to the largest cells, and flew through them repeatedly, for a couple of hours at a time, moving as needed, at 500' intervals. Fly through the cell, make a hard turn right, hard steep turn left to get back into the storm as rapidly as possible, and do the run in the opposite direction. Again, and again, and again. For months at a time. And it wasn't bad judgement, but scientific research with meteorologists on board, banks of computers and sensor information, and a full team on the ground directing each mission, which was in concert with. multiple other aircraft. In fact, the largest project of its kind, at the time.

We took a lot of lightning strikes, dealt with a lot of turbulence enough to bring on the shaker and pusher and on occasion roll us inverted, and once broke my headset and one of my headsets I'd loaned to a sensor operator.

I'm a long time active mechanic in addition to a pilot, and have been for decades; I worked on the Lears as well as flew them. I operated them for several employers, domestically and internationally, including Saudi Arabia and places north.

I've taken those aircraft places that would have wrinkled wings on a citation and broken other aircraft. They flew well and performed well, especially given their simplicity. They performed well at slower speeds as well as high, and they did well with a lot of gear hanging off the outside of the aircraft, too.

We didn't have the severe corrosion issues that we had in Sabreliners, which plague the type throughout the system. Lears are made to go fast, but a lot of what we did had to be flown at slower speeds due to the external stores; the airplanes handled well at lower speeds, and we carried a lot more ice than I'd have guessed they could handle, given the rapid buildups we experienced, and the fact that out operations frequently required operating in the -15C range at the maximum icing locations.

The one issue that I experienced wasn't the result of a storm or environmental damage, but that caused by a project scientist. Onboard data was downloaded by a team after we returned from a hop, and that required powering systems, which we did with an extension cord rather than powering the whole aircraft. The systems were powered in flight by the aircraft. To do a download required 115 VAC input, and one morning when we weren't there, a lead scientist grabbed a cord from the wrong shed and plugged it into the aircraft...with 220. He not only fried some of his equipment, but because the system interfaced with the aircraft , we began having issues crop up repeatedly from the damage he did. The airplane was never designed to handle stupidity.

As a design, Bill Lear did well. The early 20 series, especially the 23, were absolutely haphazard; ever 23 came out differently, with no standardization in instrument layout, etc. A series of changes occurred in the 24 and in the 25, and the emergency pressurization system from the 20 series remained into the 35 for the early serial numbers; it may have been this (and several other factors) that caused the Payne Stewart incident. Lears are intuitive and easy to fly, and in fact, easy to fly well. The early quirks of the 23 were fairly well ironed out by the time they reached the 30 series.

The FAA made a mistake, in my opinion, in allowing one type rating to cover the 20 and 30 series. A pilot can train and type on one, then fly the other without legally requiring additional training, and no additional certification, and that shoudln't be. The two are generally similar in systems, but quite different in performance.

The 20 series are a lot more fun.
 
nws2002
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Fri Dec 14, 2018 4:44 pm

747Whale wrote:
The FAA made a mistake, in my opinion, in allowing one type rating to cover the 20 and 30 series. A pilot can train and type on one, then fly the other without legally requiring additional training, and no additional certification, and that shoudln't be. The two are generally similar in systems, but quite different in performance.


Definitely agree there. You can even fly the 55 with the LR-JET type, and just like 20 to 30 all you do is differences training. While similar it is definitely a different airplane.
 
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tb727
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Fri Dec 14, 2018 6:11 pm

We came through a thunderstorm out over the Atlantic heading back from Bermuda late one night. We had just gone out there to pick up a patient and it wasn't there a few hours before. We couldn't get NY on the HF for any altitude changes and talked to a few planes via 123.45, they denied a climb so we plowed into it at 340. It wasn't fun. Captain hand flew it as we got thrown around like a rag doll all over the sky. Took a couple lightning strikes. Probably lasted a minute or two but it seemed like an eternity. All these years later I bet I can go walk up to that guy and just say, "Hey remember that one time...." and he would just nod and say, yep. We should have turned around, I never did get to see Bermuda during the day.

Your research has probably helped a lot in developing technology and weather predicting to help me avoid them in the big airliners I fly today, so I thank you for that, and I suppose the robustness of that little jet I don't so fondly look back at.
Too lazy to work, too scared to steal!
 
747Whale
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Re: LearJet 35/36 engine upgrade (higher thrust engine)

Sat Dec 15, 2018 7:04 am

Mostly what I got out of thunderstorm flying was a deep conviction that I don't want to ever go near another thunderstorm again.

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