Difference betweeen a Lear 31 and 31A?

[Palerider957]

Can anyone tell me what the major diffrences between the 31 and 31A are? What are the general impressions of the 31? What are real altitude, range, and profile numbes?

As always, thanks for your help.

 

[h25b]

Can anyone tell me what the major diffrences between the 31 and 31A are? What are the general impressions of the 31? What are real altitude, range, and profile numbes?

As always, thanks for your help.

The 31's that I have flown were basically 31A airframes with the old 35 avionics/systems in them. In other words, no glass, no fuel heaters, no digital nosewheel steering. They had the extended range aux. fuel tank however, but this just cuts down the already limited baggage area.

Not bad as long as you are flying pretty much all day trips, otherwise anything more than like 4 people with bags is out of the question. Not due to weight, but just cubic volume limitations.

 

[Lead Sled]

Actually, as I remember the major difference was that the 31 did not have a mach trim system and its Mmo was something like .75M. The 31A had the mach trim system and a higher Mmo. However, it's been a long time and my manuals are buried so hopefully someone can correct me if I am wrong.

I was never all that impressed with the 31 or 31A. Sure, they'll climb a bit higher than a 35, but basically if you want 31 performance out of a 35, just fly it at comparable weights. At least with the 35 you have the option of going out with 1,300 lbs (about an hour's worth) more fuel. The problem with 35s is that they're starting to get a little long in the tooth.

Both airplanes share the same miserable baggage issues - it's behind the bench seat. A 35 is a classic airplane and still has a lot of life, but I'd think long and hard about recommending one to the boss. As long as you don't need the range a Citation V would probably be a much more user friendly airplane today.

'Sled

 

[XTW]

Avatar

Great avatar Sled!

 

[h25b]

Actually, as I remember the major difference was that the 31 did not have a mach trim system and its Mmo was something like .75M. The 31A had the mach trim system and a higher Mmo. However, it's been a long time and my manuals are buried so hopefully someone can correct me if I am wrong.

You are correct on this. I have forgotten about that and it aside from the absence of digital nosewheel steering, it is one of the biggest pains in the rear of the straight 31's...

 

[Palerider957]

Thanks for everyones info.

 

[Lead Sled]

I got to play around in FlightSafety's very first 31 sim when we were there for a 35 recurrent. The instructor wasn't too kind when it came to the 31 - his thoughts were that Lear went way too far in their attempt to turn their 35 into a Citation. The 35 was a GREAT airplane to fly, but it also demanded that the pilots knew what they were doing. Their chief competition (then and probably now as well) was the Citation 500 series airplanes. The Citations fly ok, but almost every one describes them as turbojet-powered 182s for a reason - they're not very demanding.

Lear essentially put the Lear 28/29 Longhorn wing on a 35. Added those UGLY delta fins to be able to eliminate the dual yaw-damper requirement and to give it the stall characteristics of a Citation and while they were at it, they reduced the Mmo to eliminate the need for the mach trim system. In short, the eviserated a tiger and turned it into a kitten. Customers bought Lears to go fast and people didn't like the fact that the straight 31 had an Mmo of just .75M. It wasn't very long before Lear went back and reinstalled the mach trim system so thay they could raise the Mmo back up to where it is now. (FYI - the Mmo limit is due to the horizontal tail design, not the wing, and is shared by all 20 and 30 series Lears.)

I alway thought that it was strange that Lear put the delta fins on their airplanes as a bandaid fix so that they could enhance their stall recovery and yaw dampening qualties - similiar to what Beech had to do to the 1900. The Lear 45 was touted as a "Clean Sheet" design. If it truly is, why keep the bandaids? Why not design a proper tail for the new airframe? You can probably tell, I'm not a real fan of the current Lear line.

'Sled

 

[h25b]

I got to play around in FlightSafety's very first 31 sim when we were there for a 35 recurrent. The instructor wasn't too kind when it came to the 31 - his thoughts were that Lear went way too far in their attempt to turn their 35 into a Citation. The 35 was a GREAT airplane to fly, but it also demanded that the pilots knew what they were doing. Their chief competition (then and probably now as well) was the Citation 500 series airplanes. The Citations fly ok, but almost every one describes them as turbojet-powered 182s for a reason - they're not very demanding.

Lear essentially put the Lear 28/29 Longhorn wing on a 35. Added those UGLY delta fins to be able to eliminate the dual yaw-damper requirement and to give it the stall characteristics of a Citation and while they were at it, they reduced the Mmo to eliminate the need for the mach trim system. In short, the eviserated a tiger and turned it into a kitten. Customers bought Lears to go fast and people didn't like the fact that the straight 31 had an Mmo of just .75M. It wasn't very long before Lear went back and reinstalled the mach trim system so thay they could raise the Mmo back up to where it is now. (FYI - the Mmo limit is due to the horizontal tail design, not the wing, and is shared by all 20 and 30 series Lears.)

I alway thought that it was strange that Lear put the delta fins on their airplanes as a bandaid fix so that they could enhance their stall recovery and yaw dampening qualties - similiar to what Beech had to do to the 1900. The Lear 45 was touted as a "Clean Sheet" design. If it truly is, why keep the bandaids? Why not design a proper tail for the new airframe? You can probably tell, I'm not a real fan of the current Lear line.

'Sled

While I don't share any particular fondness for the Learjet 31a. All of these "bandaid fixes" that you mentioned do work. They did achieve the desired outcome and the 31A does what it was supposed to do.

As for the Delta fin, it fixes the main complaint I had with the 35. I hated fighting those dual yaw dampers and it is nice to have an airplane that is now so stable it no longer even really needs the dampers.

When speaking of the 31A they didn't take the tiger out of anything..

 

[Lead Sled]

While I don't share any particular fondness for the Learjet 31a. All of these "bandaid fixes" that you mentioned do work. They did achieve the desired outcome and the 31A does what it was supposed to do.

As for the Delta fin, it fixes the main complaint I had with the 35. I hated fighting those dual yaw dampers and it is nice to have an airplane that is now so stable it no longer even really needs the dampers.

When speaking of the 31A they didn't take the tiger out of anything..

The way they put the "tiger" back into the kitten was to limit its weight. In an airplane of that size, 1300 lbs is significant. The 35 is a real scooter if you limit its weight to 17,000 lbs.

I've got 3,000 hours in Lear 35s and I never had an issue with the dual yaw dampers. Perhaps it could be an issue for some operators, but we rode our airplane hard (for corporate) and never had a dispatch issue in 6,000 hours. That's good enough for me.

'Sled

 

[Gulfstream 200]

Sled I love that avatar!

 

[Lead Sled]

Sled I love that avatar!

I love your signature line!

'Sled

 

[LearDriver]

A few more differences....

The straight 31 that I flew did have... partial glass, fuel heaters, and did have digital variable authority nosewheel steering, but did not have the extra 75 gallons in the trunk (4124 lbs total)... so I guess it all just depends on the plane. There is a 31XR that holds the extra 500 lbs. Some Lear 31's are, red lined restricted to .78, as is mine, as compared to 31A MMO. Although, with the limited fuel pulling it back to .70 in the upper forties to go anywhere very far was quite common.

Some more differences ---- The straight 31 does have a different autopilot as well (the 530 AFCS). The pitot static system has minor differences. The 31A has has an electric windshield (good improvement). The mach trim as previously mentioned. The electrical distribution busses, both ac and dc are different also. Also, most of 31A's will already have the Raisbeck locker installed. Which I would have liked to have had if only a place to put crew bags.

The 31 is a great plane for shorter missions. It was a joy to fly, but going from Dallas to LA is usually not going to work in the winter time. My only complaint was that I wished that it held just a bit more fuel. It's not a whole lot better than a twenty series on range. You have to get it up to altitude. It will climb straight to the mid 40's without the weight restriction and wing buffet issues that the heavier lears have. Burns 1600 first hour, 1000 second or as low as 850 an hour total at fl 470 with the speed back (.70 - .72)..... Landing with about 800 lbs after a three hour flight. If you are going back and forth across the country the older 35 or an under powered 55 would probably be the way to go if you want to go with a lear. Or heck,,, money is no object, right... go for the LR60. Anyways, hope this helps a little.

 

[LearDriver]

Customers bought Lears to go fast and people didn't like the fact that the straight 31 had an Mmo of just .75M. It wasn't very long before Lear went back and reinstalled the mach trim system so thay they could raise the Mmo back up to where it is now. (FYI - the Mmo limit is due to the horizontal tail design, not the wing, and is shared by all 20 and 30 series Lears.)


'Sled

Seems awkward when the all the Twenty series has .82 limit without mach trim. The tail is definitely the weakest link, but the Mmo limiting factor on twenty series was the fact that it has the power to accelerate to mach buffet in cruise. As I understand it Vmo is what would be limited by the tail design. That's why on some twenty series lears you could accelerate to 359 knots above 14000 on a LR25 D model (50kts faster approx). When Lear put the century III wing w/ softflite on the 25D they also beefed up the tail.

.75 or .82 ---- It never seems fast enough does it??? : )

 

[some_dude]

As I recall, mach trim only is a factor for hand flying. The 25D could go to .83 (or maybe .82, I can't recall) with the autopilot on, but only .74 when hand flying. This was because it didn't have mach trim.

Maybe it's the stick puller which is missing in the 31?

Incidentally, I've only flown a 31A (and not much in that), and I loved it. Modern avionics and autopilot in a Lear? Good times!

 

[ultrarunner]

Can anyone tell me what the major diffrences between the 31 and 31A are? What are the general impressions of the 31? What are real altitude, range, and profile numbes?

As always, thanks for your help.

The main differences:

TR's standard

Completely integrated EFIS system and FMS

Single point refueling

Those are the primary differences.

 

[UGAflyer]

The main differences:

TR's standard

Completely integrated EFIS system and FMS

Single point refueling

Those are the primary differences.

Our straight 31 has single point..so i'm not sure about that one. Maybe that isn't standard on the earlier ones?

 

[ultrarunner]

Our straight 31 has single point..so i'm not sure about that one. Maybe that isn't standard on the earlier ones?

Ya know, now that I think about, I think just the first 15 or 20 straight planes didn't have it. Then offered as an option, then became standard on the 31a.

I liked the straight 31. But like many owners, they naturally wanted it to fly missions for which it wasn't designed.

And trying to make south FL in the winter with a full load of folks often required a fuel stop. Oh well, no sweat off my back.. I didn't buy it...I just flew it...

 

[Lead Sled]

Ya know, now that I think about, I think just the first 15 or 20 straight planes didn't have it. Then offered as an option, then became standard on the 31a.

I liked the straight 31. But like many owners, they naturally wanted it to fly missions for which it wasn't designed.

And trying to make south FL in the winter with a full load of folks often required a fuel stop. Oh well, no sweat off my back.. I didn't buy it...I just flew it...

I really enjoyed flying the Lears. (Coast-to-coast and border-to-border plus the length of Canada three or four times a month for 8 years.) However, the happiest day of my life was the day we sold that airplane. It took me months to be able to get my head straight - it had developed a definite lean to my right shoulder. My chiroprator was bummed to - we were finally able to closeout my open ended workman's comp claim from having to drag all of the bags down that skinny isle and throwing them behind the seat.

'Sled

 

[LJDRVR]

That breings to mind a good joke:

How do you tell a Lear crew? (It's not the answer you think.)

• They drag their suitcases over the furniture in the FBO. :laugh:

 

[ultrarunner]

The 31's are the perfect plane to fly 4 folks with duffle bags 800 miles to a 3000 foot runway.

That's about it.