Lab Rat in a Learjet
Flying as a evaluation pilot assessing an upset recovery guidance system in the development process.
It seemed innocuous enough—an email from Nathan Richards, Ph.D., a reader of our sister publication, IFR magazine, asking if someone would be interested in flying a Learjet in-flight simulator as part of a project his employer, Barron Associates, was doing on upset recovery. I wasn’t sure what an in-flight simulator was, but I’ve been very interested in the research that’s being conducted on in-flight loss of control and upset recovery and I’ve had an abiding affection for 20-series Learjets ever since I spent a little time as a copilot freight dog in a 23 and 24B many years ago. When I found out that the Dr. Richards’ project was tied in with NASA (the first “A” stands for Aeronautics), my interest got even stronger. When I learned that the flight would be made at the nearly legendary Calspan operation, the idea of not going became intolerable.
A Little Background
What is now Calspan corporation was born during World War II as a part of the research lab at Curtiss-Wright’s airplane division—think P-40 Tomahawk/Warhawk series and C-46 Commando transport—to do cutting-edge aeronautical research. Following the war it was donated to Cornell University and became Cornell Aeronautical Laboratories. In the early 1970s it was reorganized as a for-profit corporation, but has not deviated from its mission to do aeronautical research. A few of its developments have been the crash-test dummy, the automotive seat belt, Doppler weather radar, terrain-following radar and something I’d been reading about since I was a kid—the ability to make an airplane simulate the handling characteristics of another in flight. Calspan calls it Variable In-Flight Stability. One of the most notable was taking a Convair 340 (modified with turboprop engines) and hanging another nose and cockpit in front of and below the standard-issue nose and installing additional aerodynamic control surfaces so that the resulting airplane could simulate, in flight, the landing approach profile of the Space Shuttle.
Starting in 1979, Calspan stepped up its in-flight simulation chops by going to Learjet and purchasing a Lear 25B that had been a company test airplane. To shorten the story, that Learjet, and three others, now have a standard control system for the left seat but for the right seat pilot there is a fly-by-wire control system that, through appropriate computer integration, can duplicate the handling, stability and control and control response of nearly any jet transport category airplane. The Lear was chosen because its wing was originally used on a Swiss fighter, making it capable of handling fairly high accelerations in normal use.
Calspan now uses its Learjet in-flight simulator fleet for training pilots in upset recovery and supporting research into upset recovery and prevention.
That's where Barron Associates enter the picture—Dr. Nathan Richards and his team have developed upset recovery guidance software that (paraphrasing) gives a pictorial reference for a pilot that recommends appropriate yoke, rudder and power lever inputs to recover from any sort of inflight upset/loss of control event that may be experienced. While Barron Associates engineers have developed automatic upset recovery software that is used on UAVs and, it appears to me, would work on human-occupied airplanes, the cost of certificating such devices under FAR Part 23 and 25 is simply eye-watering. Accordingly, it is proceeding along the lines of an installation that would appear on the Primary Flight Display immediately upon the system becoming aware that an upset is imminent (think how fast airbags sense and deploy) and would provide avoidance and/or recovery guidance to the pilot. Sort of an “Excuse me, I know you’re really jammed up, things are rapidly going south with the airplane and you’re appropriately terrified, but if you’ll do this with the controls, you can return to straight-and-level cruise with a minimum of fuss.” Software that makes recommendations to pilots is far cheaper to certify that software that tells pilots what to do or takes over flying the airplane.
Barron teamed with Calspan to put the upset recovery guidance system into one of the Lears, sorted out the inevitable glitches and then sought evaluation pilots to see how they used the system and reacted to it—lab rats to run the maze as it were.
The evaluation process thus far has consisted of a number of steps as Dr. Richards and his colleague scientist/engineer, Neha Gandhi—who was deeply involved in creating guidance and control algorithms for the system—obtained objective and subjective feedback from pilots flying it and progressively tweaked it. I also learned that there had been substantial interaction with NASA's technical representative to the overall program, Dr. Christine Belcastro, and an expert "pilot-in-the-loop" systems interaction team at Systems Technology, Inc. lead by David Klyde in the process of getting the "speed" of the guidance cues to be appropriate.
Testing the guidance system in as real world a manner as possible involved finding a spectrum of pilots who might be expected to fly it in service and then having them fly a profile involving upsets and unusual attitudes based on events that had lead bizjets and airliners to grief. Each profile would be flown twice—randomly selected—and recovery would be attempted with and without the guidance presentation. To make things as real as possible, the evaluation pilots would only be given a limited introduction to the system—a few minutes in the airplane on the ground in simulator mode—so as to not prep them for what was coming. The evaluation pilots were given an advance introduction to the Recovery Quality Rating Scale—based somewhat on the Cooper-Harper rating scale used by test pilots to quantify aircraft handling. The evaluation pilot would be required to turn her or his thoughts about how easy or difficult, and stressful, it was to recover—or not—from an upset into a rating on a 1 to 10 scale, with 1 being “excellent/highly desirable” and 10 being unable to recover from the maneuver.
At the appointed time I presented myself at Calspan’s facility on the Buffalo/Niagara Falls, New York airport and met Nathan Richards. He introduced me to Neha Gandhi and I learned that she and I had both gotten degrees from the same university, a few years apart, and spent a few moments in college town nostalgia. She explained that she would be in the jump seat watching and recording my response to each upset scenario and getting immediate verbal feedback from me on the Recovery Quality Rating Scale as well as my impression of such things as the rate/speed that the recovery guidance presentation called for control inputs, the ease of using the guidance, comparisons between the ease of recovery with and without guidance and any comments that came to mind in the heat of battle.
Calspan engineer/scientist Martin Koschel would be the flight test engineer—in the cabin monitoring the proper functioning of the fly-by-wire inflight simulator control system and generally making sure that we who were up front wouldn’t do anything foolish. Calspan VP and former Air Force F-16 pilot, Brian Ernisse, would be the pilot in command and in charge of the overall conduct of the flight. He would advise Gandhi and Koschel of each upcoming maneuver verbally, using a code so that I would not know what was coming. I was told that I would be wearing an instrument hood throughout the evaluation process and that some of the upsets would be created by the computer running the inflight simulator software and some would be traditional put-your-head-down-and-don’t-peek-until-I-say-to-take-the-airplane unusual attitudes every pilot has done since primary training.
I was told that the default condition of the airplane would be level flight at 12,500 feet (we’d be in a MOA over Lake Ontario) at 250 KIAS. We’d start each scenario from that condition and I’d endeavor to return the airplane to it. The Lear had been modified and was subject to certain waivers/exemptions that allowed us to operate in a flight envelope that where we did the things we needed to do without violating FARs. However, there were parameters for each upset event and if I did not recovery the airplane before hitting one of them—such as indicated airspeed, pitch or bank angle—the system (or Ernisse) would shut off my controls and the airplane would revert to the normal Learjet control system that only Ernisse could operate. The system was set up so that when the right seat fly-by-wire controls were active he could not control the airplane and vice versa. Should Ernisse become incapacitated Gandhi, Koschel or I could activate the fly-by-wire system and I could land the airplane.
Because upset recovery may require large, rapid power lever movements, I expressed my concern about doing so as the maintenance in the Lear freighters I flew had been lousy and one of the first things drilled into my head was to move the power levers very slowly. I had slipped up once at altitude and flamed out an engine. There was laughter around the table and I was told that Calspan had very good maintenance and I could move the power levers as fast as I wanted. It turned out that they weren’t kidding.
It Happens Fast
I was told to expect to do poorly when attempting the upset recoveries. Even though I would know something bad was going to happen, there would very little time to work through the normal startle response, evaluate what was going on and do the right thing to get the airplane back to where it belonged and keep it there. Things happen fast in a jet and there may be damage that requires figuring out what ongoing control inputs are required to keep things under control.
The next step was to introduce me to the guidance system itself. Lear N102VS was in a corner of the Calspan hangar next to some impressive airplanes I agreed not to photograph or talk about. Plugged into ground power, its systems were alive and the in-flight simulator system was set up to duplicate the handling of a transport-category jet. On the Primary Flight Display the guidance system presented as a magenta/pink chevron that represented the desired position of my yoke, a magenta box represented the desired rudder position and a set of red guides represented the desired power lever position (it did not command splitting the power levers although doing so helped with some of the upset recoveries such as rudder and aileron hardovers). A blue chevron depicted the actual position of the yoke; a blue dot the actual position of the rudders and a green triangle the actual power lever position. In responding to information provided by the upset recovery guidance program, the idea is to fly position the yoke, rudders and power levers so that the green and blue indicators are kept in the magenta/pink chevron/box/guide. Here’s a brief video of it in action.
I was told that most upset recovery training programs for jets call for the pilot’s feet to be left on the floor even though proper rudder input can and will increase the odds of successful recovery. The important word being “proper,” as it is not unusual for a pilot to apply too much rudder in the excitement of the moment—which has lead to the loss of the vertical stabilizer and aircraft. I thought back to the November 2001 Airbus crash on Long Island in which the flying pilot applied too much rudder in response to a wake turbulence upset and removed the vertical stabilizer from the airplane.
When the rudder guidance was explained to me, I felt that the display was backwards—counterintuitive to me. Everything else made perfect sense.
I was given less than two minutes to get used to the PFD display, “flying” the Lear/transport-category jet in level flight, turns, climbs and descents. I was then presented with two or three upset scenarios and worked to position the controls to fit into the chevrons for the recoveries. Not wanting me to learn any more about the handling of the aircraft or the functioning of the guidance, the system was powered down and I learned that when the fly-by-wire system is off, the copilot’s controls truly are disconnected, they flop around like overcooked pasta.
The next step was a detailed safety briefing that started in the airplane and moved to a conference room. It was one of the most professional and complete I’ve ever experienced. I was again told that the upset scenarios would reflect actual aircraft accidents and would include runaway trim nose up, autopilot runaway nose down, aileron and rudder hardover, icing and the classic pilot distraction events—nose high with airspeed decreasing and nose low in a steep bank. There were moments of humor—because every pilot who ever tried to squeeze juice out of a control yoke while flying instruments looks funny wearing an instrument hood, comments were made about the fact I’d be wearing one. I was intrigued to find that the hood of choice was the $11.00 Jiffyhood, the type that I own because it works so well, doesn’t interfere with your scan if you have bifocals and was rated the best instrument hood back in 2013 by our sister publication Aviation Consumer.
In the airplane, we picked up our instrument clearance and blasted into the overcast (Surgeon General’s Health Warning: Learjet acceleration on takeoff is addictive and may lead to foolish behavior such as deciding to fly for a living). In moments we were well above the thin cloud layer, in the MOA with a block altitude clearance and I was donning the hood. Ernisse activated my flight controls and had me briefly make a couple of turns, a climb and descent, then started the exercise.
During the next hour (it felt like about 15 minutes) I experienced some upsets that made perfect sense and were easy, in my opinion, to recover from, and some that were fiendishly difficult—and which I could not sort out in time to avoid blowing through the “disarm that idiot’s controls” parameters without having the guidance display on the PFD to help me rectify matters.
The easy ones included 25 degrees nose down and a vertical bank—power levers to idle, roll wings level while not letting the trim load up the gs as a rolling pull up doesn’t win friends and positively influence airframes and then pull up at about 2.5 g to return to altitude and level cruise.
There was a subtle one that, without guidance, I couldn’t figure out before things went down the slot. The scenario was slowing to 180 KIAS for downwind on a crummy weather but good enough to make a visual approach day. As I slowed through about 220 knots, the airplane began rolling left and right despite my best efforts to figure out why it was doing so and trying to stop the excursions with rudder and aileron. In a matter of seconds the system had decided that the airplane was departing controlled flight and returned control to Ernisse. As I answered Gandhi’s questions on the scenario and gave the recovery a rating of 10, I racked my brain trying to figure out what the heck it had been. Later I was told it was airframe ice and I’d stalled the airplane. Sound of forehead smack. It suddenly made complete sense and I felt like a complete moroon for not getting the nose down and adding power. As the scenarios rolled around I got that one again with the guidance on—recovery was a piece of cake, I just pushed on the yoke until the blue chevron was within the magenta one and pushed the power levers up as recommend in the display.
I will solemnly state that an aileron or rudder hardover is quite a ride and recovery takes everything you’ve got. There were times that I had both hands on the yoke to apply full aileron and had to figure out how to let go briefly with my left hand to split the power levers to take advantage of asymmetrical thrust while wondering if I could do it fast enough because I wasn’t sure whether the control forces would be too much to handle one handed. I could have called for the nonflying pilot to handle the power levers but I was simply curious to see if I could do it myself with the control forces involved.
Broken Airplanes Don't Fix Themselves
While I knew intellectually that an aileron or rudder hardover wouldn’t fix itself once I’d wrestled the airplane back into a semblance of level flight, my brain wouldn’t accept it—and I kept reducing the control input and having the airplane again start to roll and pitch down. Reading and thinking about an upset is no substitute for doing it for real. After the flight, as I was kicking myself for not keeping the needed control input in place, I realized that in all of my training and recurrent training over the years—airplane or simulator—once I got the airplane back to level flight the instructor stopped the exercise. I never had to try to continue to fly an airplane with a jammed control for any length of time. That’s something to consider when talking about the real world of unusual attitude recovery, where the airplane is probably intact, versus upset recovery, where the upset may have been caused by a control surface or trim tab that has moved and is going to stay moved. Upset recovery is more than finding level flight, it’s continuing to control an airplane that may be marginally controllable and get it onto a runway. I found the guidance software to help with that process a great deal. It recommended maintaining control inputs. When I did what it recommended, it helped me overcome my tendency to relax the inputs.
I found I had trouble with a nose up trim runaway event. I’m a piston-engine pilot mostly, so I simply shoved on the yoke as hard as I could and called for secondary trim. That didn’t work well. There is a high risk that the airplane will stall. Ernisse, who wore that Lear like a second skin, mentioned to me that jet training calls for immediately putting the airplane into a steep bank—that is the way to lower the nose. It also takes advantage of the nose up trim—it puts you into a turn—and you’re less likely run out of airspeed. In my opinion, that needs to be taught in piston-engine courses. I’m going to be talking with some CFI friends about the subject.
Way too soon the last upset scenario was complete and I’d answered Gandhi’s questions about my reactions to it. Ernisse disabled my set of controls, advised ATC we were done and got a vector and descent to set up for the ILS into home plate.
Once the jet was in the chocks Dr. Richards met Ernisse, Gandhi, Koschel and me in a small conference room for the debrief. The purpose was to get any further input I had on the upset recovery guidance software and presentation. While I got some feedback on my flying and some suggestions, it was incidental to the remainder of the conversation. My conclusions on the guidance? I found it to be extremely helpful. The two (that I recall) upsets from which I was unable to recover within the parameters involved raw data—no guidance. With the guidance on, and especially as I got more used to scanning it to see all three pieces of guidance—it took me a bit to include the power guidance in my scan—I was able to recover from each upset within the parameters. I found the rate at which the guidance called for control inputs to be intuitive—I’m guessing a lot of skull sweat had already gone into that issue. I still found the rudder guidance to be backward to how I think, so I had to spend some time making sure that I was making the correct rudder input before I could worry about the appropriate magnitude.
Being a lab rat in these circumstances was a heck of lot of fun and educational for the rat, although there’s the sense of wishing I could have done better than I did—why couldn’t I figure out and recover from all of the events within the parameters? Intellectually, I know that the upsets being duplicated killed people—that’s why they’re being duplicated—some good pilots couldn’t recover and died. Emotionally, I wanted to be perfect. After all, every pilot wants to ace every checkride. I came away wiser and with even firmer opinions about upset recovery training.
Make Upset Training Realistic
I’ve done upsets and unusual attitude recovery for decades in just about every type of ground-based simulator made as well as many different aerobatic airplanes. Simulators are great, but they have the shortcoming of not being able to instill the level of startle and “what the devil is happening?” of a sudden change in g load and yaw that occurs in the airplane in flight. Further, most aerobatic airplanes simply do not duplicate the need for massive, continued control deflection that takes a fair amount of physical effort that is required in transport airplanes when things get ugly. In most akro birds it’s a flick of the wrist to restore level flight—although the closest thing I’ve flown to duplicating what’s involved in recovering from an upset in a transport category airplane after Calspan’s Lear is the modest Cessna 150 Aerobat—because it requires very large and prolonged control inputs. After my session in Calspan’s Lear I’m even more convinced that upset recovery training should start in the simulator and then move into something that closely resembles the handling of the airplane the pilot regularly flies.
I’m also excited about the potential for upset recovery guidance presentations such as Barron Associates is developing. Once in the “Ohmigawdwe’regonnadie” moment as an upset violently begins and your head smacks the side of the cockpit, having a display suddenly appear that you know is telling you where to put the yoke, rudders and power levers would, in my opinion, be a major confidence builder that will improve the odds of getting the airplane collected and safely returned to the planet at the location the pilot desires. I hope that this project becomes reality and that it trickles down to the piston general aviation world.
Finally, I came away having once again experienced the sheer pleasure of working with scientists and engineers. In a world suddenly peppered with alternative facts, I was reminded that scientists and engineers cannot afford the luxury of making things up—they take nothing for granted, test everything and then test again to assure that the results they achieve are accurate and can be duplicated. They live in a world of hard, exacting work and small steps toward certainty. Thank you Dr. Nathan Richards, Neha Gandhi, Martin Koschel, Brian Ernisse, Barron Associates and Calspan for the opportunity to be a lab rat for a while. I hope someday I can say that I had a tiny little something to do with a successful upset recovery guidance system that is in widespread use.
Rick Durden is a CFII and holds an ATP with type ratings in the Douglas DC-3 and Cessna Citation. He is the author of The Thinking Pilot’s Flight Manual or, How to Survive Flying Little Airplanes and Have a Ball Doing It, Vols. 1 & 2.