Swept Wing Jets

[ZapBrannigan]

I think what people are missing is that in normal flight conditions most airplanes are easy enough to fly. Where the early Lears (and other swept wing airplanes) tend to bite you is when you inadvertently venture too close to the edges and THEN exercise inattention or poor technique. There would not be any upset recovery training if pilots never inadvertently found themselves in an upset condition. One highly regarded provider in Mesa, Arizona frequently cites the example of cheating the base to final turn with rudder. An inexperienced pilot who ends up slow and cross controlled, might find themselves in an upset without the altitude to recover (if recovery is even possible). The early Lears would have exacerbated the problem with spoileron deflection. I don't think these machines are particularly difficult to fly, but they're certainly not going to have Cessna 172 stall characteristics. You'll be way behind the power curve, with a slow spool time, little roll control, and an elevator which "may" be partially in the shadow of the fuselage. I'm no aerodynamicist (clearly) but I respect the airplane.

It's not the most unforgiving airplane I've ever flown (That honor goes to the Jetstream) but it is a slick machine that can easily get away from you if you are inattentive.

 

[Hacker15e]

I'm not sure anyone would have the cajones to intentionally stall a transport category jet so I'm not sure why there would be a disparity between swept/straight wing airplanes?

You can bet that Boeing did exactly that when they developed the 707, 727, 737, etc.

I spoke to Lew Wallick (the chief test pilot for Boeing on the 727, 37, 47, etc) back in the late 80s, and he said that every one of those models had been rolled a'la 367-80.

 

[Hacker15e]

They are an entirely different airplane... all together!

"Its an entirely different airplane...."

 

[inigo88]

You can bet that Boeing did exactly that when they developed the 707, 727, 737, etc.

I spoke to Lew Wallick (the chief test pilot for Boeing on the 727, 37, 47, etc) back in the late 80s, and he said that every one of those models had been rolled a'la 367-80.

I don't doubt it. They rolled the concorde too, and not just the BAC test pilots either.
"I've taken it one way Brian, you better unwind it."

 

[A-300F4-622R]

I think what people are missing is that in normal flight conditions most airplanes are easy enough to fly. Where the early Lears (and other swept wing airplanes) tend to bite you is when you inadvertently venture too close to the edges and THEN exercise inattention or poor technique. There would not be any upset recovery training if pilots never inadvertently found themselves in an upset condition. One highly regarded provider in Mesa, Arizona frequently cites the example of cheating the base to final turn with rudder. An inexperienced pilot who ends up slow and cross controlled, might find themselves in an upset without the altitude to recover (if recovery is even possible). The early Lears would have exacerbated the problem with spoileron deflection. I don't think these machines are particularly difficult to fly, but they're certainly not going to have Cessna 172 stall characteristics. You'll be way behind the power curve, with a slow spool time, little roll control, and an elevator which "may" be partially in the shadow of the fuselage. I'm no aerodynamicist (clearly) but I respect the airplane.

It's not the most unforgiving airplane I've ever flown (That honor goes to the Jetstream) but it is a slick machine that can easily get away from you if you are inattentive.

20 series Learjets do not have spoilerons. CJ-610 has a fast response time for a jet engine.

 

[MikeD]

One highly regarded provider in Mesa, Arizona frequently cites the example of cheating the base to final turn with rudder. An inexperienced pilot who ends up slow and cross controlled, might find themselves in an upset without the altitude to recover (if recovery is even possible). .

Over/undershooting final turn in a swept wing jet is no laughing matter. Especially since a stall in one of these doesn't manifest itself with any kind of nose fall-through like a straight-wing does. All you get (as you know) is the 'elephant dance" on the wings, and a horrendous descent rate occuring and getting worse, with the nose still pointed where you have it.

CJ-610 has a fast response time for a jet engine.

It's military cousin the J85 is the same way. Non-AB J85s were used in the A-37 Dragonfly, and they gave that plane a good boost of power.

 

[Bumblebee]

"Its an entirely different airplane...."

altogether

...but that's not important right now....

 

[mshunter]

Just don't get it slow. My Jet time comes from a smathering of Lears, and a little bit of straight wing CE500/560's. Flying an approach in gusty x-winds with a Lear55 who yaw dampers are both out, well, you end up slipping and coming in a few knots fast to keep it dutch roll in check. Not a big slip, just a resting foots weight of pressure on one pedal. In the 550/560, I felt like I was going to fall out of the sky coming in on approach it was going so slow! Vref of 104 knots or something like that on my first landing and the thing still floated half way down a 6000ft runway!

But, either can be taught. My very first jet experience was a Lear31. I miss the hell out of that rocket ship! So, as long as you/your company gets the proper training, Look at what they do with the military guys.

 

[Hacker15e]

Over/undershooting final turn in a swept wing jet is no laughing matter. Especially since a stall in one of these doesn't manifest itself with any kind of nose fall-through like a straight-wing does. All you get (as you know) is the 'elephant dance" on the wings, and a horrendous descent rate occuring and getting worse, with the nose still pointed where you have it.

The worst part is, depending on conditions, it is possible to get into an unrecoverable sink rate very close to the ground even without "elephants dancing on the wings" -- which is why there are AOA gauges and VVIs/VSIs. That's the insidious -- and dangerous -- part.

 

[A-300F4-622R]

The worst part is, depending on conditions, it is possible to get into an unrecoverable sink rate very close to the ground even without "elephants dancing on the wings" -- which is why there are AOA gauges and VVIs/VSIs. That's the insidious -- and dangerous -- part.

Buddy of mine was a T38 IP back in the early '70s and IIRC, he said that there was a time during the final turn where the rate of descent of the jet was about opposite the vertical velocity of the ejection seat and if you had to eject during the final turn you'd basically just plop out of the jet and have little to no upward vertical velocity.

 

[Hacker15e]

Buddy of mine was a T38 IP back in the early '70s and IIRC, he said that there was a time during the final turn where the rate of descent of the jet was about opposite the vertical velocity of the ejection seat and if you had to eject during the final turn you'd basically just plop out of the jet and have little to no upward vertical velocity.

It is actually even worse: there are descent rates possible in the final turn which the T-38 ejection seat cannot overcome at all. It isn't really that great of a seat compared to current designs.

The real problem is that "ground rush" -- the perception that you are rapidly approaching the ground -- doesn't take place until you are at an altitude which equals 10% of your VVI. By the time you recognize you are in a big sink rate, you are too low and descending too fast for the ejection seat to get you clear of the airplane and deploy/inflate your parachute before you, too, impact the dirt.

 

[Cessnaflyer]

It's like jumping in a falling elevator.

 

[Springer]

Fully stall most commercial transport aircraft and it will not end well.

A buddy who is a test pilot for another aircraft manufacture, was invited to fly the 787 and did stalls without any adverse results. Was very comfortable with the jet and felt he "could most anything with it."

 

[Cessnaflyer]

A buddy who is a test pilot for another aircraft manufacture, was invited to fly the 787 and did stalls without any adverse results. Was very comfortable with the jet and felt he "could most anything with it."

That's because of computer protection.

 

[Hacker15e]

A buddy who is a test pilot for another aircraft manufacture, was invited to fly the 787 and did stalls without any adverse results. Was very comfortable with the jet and felt he "could most anything with it."

I find such close parallels between this discussion and the "afraid of the airplane" thread.

The whole "don't stall a swept wing jet!" boogeyman is something that is built up because people don't go do it. Yes, there can be adverse effects of a stall in some airplanes (the T-6 comes to mind), but the characteristics are known and can be trained to.

T-6 accelerated stall (not my video):


I think some folks think that stalls are not practiced in some aircraft (like transport category airplanes) is because they'll crash or something if they try. Not training to that has more to do with logistics and economics than it does risk.

 

[z987k]

I find such close parallels between this discussion and the "afraid of the airplane" thread.

The whole "don't stall a swept wing jet!" boogeyman is something that is built up because people don't go do it. Yes, there can be adverse effects of a stall in some airplanes (the T-6 comes to mind), but the characteristics are known and can be trained to.

T-6 accelerated stall (not my video):


I think some folks think that stalls are not practiced in some aircraft (like transport category airplanes) is because they'll crash or something if they try. Not training to that has more to do with logistics and economics than it does risk.

Ya, I've taken every aircraft I've ever flown into a fully developed stall during training. I don't really plan to change that anytime soon, even if I have to do it in a sim.

 

[TFaudree_ERAU]

Flying an approach in gusty x-winds with a Lear55 who yaw dampers are both out

They BOTH went out enroute...right?

Right??

 

[TFaudree_ERAU]

His reply was "what do you care, you're probably never going to see the cockpit of one.."

So. Was he right?

 

[seagull]

I have no idea where this notion of the stall being the issue with swept wings came from. Most all the transport jets have very docile stall handling. The docile stall has nothing to do with FBW controls, either. Some of the older ones could get a tip stall, which is not great, but that is not true of the newer ones. Now, if you are not in a normal configuration, then there might be surprises. The other problem is that the stall buffet itself can sometimes cause damage to surfaces. The issues that can kill you i are not the stall, but has to do with flat lift-curve slopes, large pitch transients and the high sink rates that can be develop, plus high altitude and mach effect issues.

In answer to another poster, knowledge is a big part of it, so understanding the aerodynamics helps, but when something happens fast, you have to be able to respond faster and there is no time for a slow cognitive process. Using Gary Klein's term, you need to have Recognition Primed Decision making (RPD), and that only comes from good and thorough training and experience. I know of no civilian training program that covers the topics adequately.

 

[Bandit_Driver]

Hacker I would not try and deep stall a 727. A deep stall in the 727 will most likely stall the tail and flame out the engines as well and will result in the aircraft falling out of the air at nearly 20,000 fpm. Without the T-tail flying good luck getting the nose to come back down. IIRC there have been a couple of DC9 and 727 crashes related to full stalls back in the planes earlier days.