The test pilot was moving the yoke 180 degrees a second swinging it wildly back and forth with some significant pitch movements as well. Given what I saw, I'm assuming NO ONE ever does stalls outside of the test flight ... looked damn near unrecoverable to me. I would guess the plane had its CG pretty far back without any paint or interior and only the pilot/co-pilot on board. Even so, it did not look like anything I'd every want to do.
So, anyone with significant Lear experience (or similar biz jets) care to comment / educate on the stall characteristics and training in these planes? Are they really as difficult to recover as it appeared on the show? Am I correct in assuming that training is just up to the stall and not complete stall / recovery outside of the test phase?
I don't have a lot of time in Lears, a thousand hours or so, but I've been through Flight Safety and Simuflite with them, and have flown them internationally for a number of years. I also did atmospheric research in them, which was primarily thunderstorm penetration and research. It was during those duties that I experienced Lear stall behavior. It was in a 35A, rather than a 60XR; different wings, and different airplanes, of course.
Pete Reynolds, Lears' primary test pilot for a number of the factory designs, had some interesting insight into Learjet deep stall characteristics. I never went there, and one doesn't even train for it in the simulator when getting a type rating, but it's interesting to know. He observed that from a deep stall condition, it takes about 15,000 to recover, and that it may not be recoverable.
In transport category training and flying transport category aircraft, we don't generally demonstrate or do a full aerodynamic stall like one does in a Cessna 172. There are several reasons for that, not the least of which is the stall characteristic of swept wing jet aircraft. Transport category aircraft (aircraft certificated under Part 25, which includes all the Lears except the 23) generally utilize warning devices such as stick shakers to announce an impending stall, and this is based on angle of attack, rather than on airspeed. If one goes to a slightly higher angle of attack than the shaker, one gets a pusher, in which the stick or column moves forward on it's own, briskly, to reduce angle of attack.
Some aircraft also utilize pullers to increase angle of attack when a mach warning activates, indicating the aircraft is going to fast.
Stall training and practice in the airplane or in the simulator is done to the shaker, generally, and one flies out of it using power. You're probably familiar with an instructor or two who had you shove the nose forward to break a stall. that doesn't really work well in transport category aircraft, where one generally gives maximum thrust and holds or slightly reduces the pitch during the stall recovery. The FAA's position on stall recovery has changed slightly in the last year or so; it used to be that altitude loss wasn't acceptable during the recovery; now, primarily as a result of what happened at Buffalo, the FAA is taking a different tack in saying that they'd rather see loss and a reduction in the angle of attack in order to get the aircraft flying again, rather than flying out on power alone. The practical standard during a check ride in transport category aircraft had drifted more toward flying out of the stall rather than simply powering out.
Powering out won't work in most light airplanes. You don't have the raw thrust, and your aerodynamics are different. In a swept wing jet, dropping the nose, especially in a stalled condition, may not be possible when fully stalled, and it can result in a rapid loss of lift, not a gain like you expect in a light airplane.
As for the aileron use, where the swept wing aircraft tends to see a developing stall occur near the wingtips first, without the use of a number of devices that have been employed, aileron deflection increases or becomes ineffective. The early Learjets (20 and 30 series) used a series of "boundary layer energizers," or BLE's, in front of the ailerons, to improve controllability at higher angles of attack, but also to reduce aileron buzz at high speeds (where mach effects caused airflow separation or disruption around the ailerons. The early leads also left that section as a straight wing, rather than swept, so that the leading edge swept back gently until in front of the ailerons, where it then straightened.
To further support better stall behavior, Learjets went through several wing changes, including changing the leading edge, and the addition of a form of stall strips along the leading edge.
The leading edge is so critical on the Learjet wing that when it's removed for an inspection (it's attached with a lot of screws), a test pilot must come from the Bombardier/Learjet factory and rectify the aircraft using dive tests.
With aileron effectiveness compromised in a stall, despite design features (stall strips, washout, airfoil changes near the wing tips, and other effects), larger aileron deflections and more frequent ones may be required. In actual practice, what's taught isn't stall recovery, but avoidance. When flying jet aircraft, we don't get that slow, or fly at that high an angle of attack.
Another difference in these, and any other swept wing jet operation that differs from what your'e familiar with in a light airplane is high altitude operations. In many aircraft, a steep turn at altitude is all it takes to stall the aircraft. At low altitudes, not a problem, but a level steep turn at high altitude can present it's own problems, and recovery can also be complicated by the changes in aerodynamics and altitude effects.
