My prayers go out to the families of the Marines lost in the Midair this past week. Aviation is dangerous, Military Aviation more so and night operations compound the danger. That is known by all participants, but doesn't lessen the loss to their loved ones. .
When I read about the accident, I had wondered if Pilot Induced Oscillation (PIO) might have been a factor. I have no idea if it was or wasn't and we may never know exactly, but having ridden that horse a number of times, I wouldn't be surprised.
Pondering subjects as every blogger does as posting deadlines draw near, I decided a bit of a flying (funny, spell check suggested "lying" there) storiy about PIO might get something in the "scheduled" queue. So it is written.....
Before I get into the specifics of what PIO is and how it occurs, a little demo of the phenomenon might help.
Given that this happened very close to the ground, I'd say the Pilot used up a Metric Crap Ton of luck in this 37 second video. (and probably soiled his drawers)
This source defines PIO as "... rare, unexpected, and unintended excursions in aircraft attitude and flight path caused by anomalous interactions between the pilot and the aircraft."
Wow...and I always thought it was caused by me hamfisting the flight controls, while the aircraft was near an edge of the flight envelope. But what do I know, I'm not an engineer.
This source states that "This is coupled with a lack of understanding of the topic by many accident investigators. In fact, outside of the aircraft certification community, there is a general lack of appreciation for these issues."
I don't know about that. Going through pilot training (back in the day when pterodactyl were used for primary training), we did quite a lot of high Angle of Attack (AOA) maneuvering. One quickly learned to use very small control inputs and wait for the aircraft to respond before changing them.
That's easy enough when you've got plenty of altitude to recover. Not so easy to do when you're close to the ground. As demonstrated by the F-8 pilot.
The first source says there are three ways to recover from PIO.
- The pilot freezes the controls
- The pilot releases the controls
- The pilot significantly reduces the aggressiveness of control input
The problem is the Pilot may not realize he's in a PIO. One of my closest (not THE closest) encounters with the Low Altitude flying record occurred at Nellis at a Red Flag. Still a LT with not a lot of flying time, I was flying an F-4E loaded with two tanks and 12 Mk-82. Just off the tanker and had let down to 500' AGL (yeah, right!) for target ingress. Doing 480 and come up to a ridge, pull up to cross, an aggressive pull back down (yes, I rolled inverted and pulled) and got the nose a little too low. Pulled back up a little harder than needed, but I had enough adrenaline flowing by now to have the strength. Nose snaps, up. I push back down, nose goes even lower. I pull....
The backseater, now has his hand guarding the stick at that point. I only could pull back a little. The airplane smoothed back out and we continued on. Debrief was somewhat intense. However, I came to realize that my Situational Awareness was not all that high during the episode. I also came to realize that having someone else in the airplane with me whose SA was very high was a blessing.
Flying Air to Air in the Eagle always involved edge of the envelope flying, which very often proceeded to outside the envelope episodes. The airplane "wanted" to fly and it didn't take much for it to regain flight. Large engines and large efficient wings made that possible.
I just had to let it fly. I learned that at Luke after I swapped ends trying to tree my IP in a 1 v 1. (He starts going straight up. You start to chase him. One or the other of you is going to run out of airspeed. That one dies.)
In any case, He goes up, I pull up trying to get the gun site on him, I run out of airspeed and the nose falls. He stands on the rudder and swaps ends behind me. But neither of us has any energy (airspeed). I'm worried because he's behind me, so I'm trying to turn. But the airplane isn't having any of that. It's just pitching up and back down with increasing magnitude. The IP relaxes back pressure on the stick, his Eagle accelerates and is flying again very quickly. I finally recognize the PIO symptoms and unload to get flying again. Too late, I spend the rest of that engagement doing the funky chicken trying to avoid (unsuccessfully) being a movie star.
The IP debriefed that engagement by telling me that my Eagle had several thousand hours of flying time on it. I didn't. When I'm in a situation like that, I should let go of the controls and let the more experienced one of us take over.
I would come to use that technique more frequently than I generally let on.
As I got more experienced, it became much easier to recognize and use the third method of recovery, I used to call this the fingertip method. I would fly the aircraft with my index finger and thumb. The thumb would be working the trim switch on the top of the stick and my index finger would handle left and right, but it would be very difficult to over control, which is the desired result.
Does PIO only occur in military aircraft? Not by a long shot.
My first source cites several examples, but this one was the worst.
My first source cites several examples, but this one was the worst.
"On 14 September 1999, a DASSAULT Falcon 900 was subjected to rapid and violent vertical load oscillations, which killed most of the passengers, after incorrect crew response to a minor pitch control malfunction. The incident occurred south of Bucharest, Romania.
Greece's Deputy Foreign Minister, who was standing at the time of the accident, was one of the passengers killed.Oh, and that last sentence, is why the airlines want your seat belt to be fastened when seated.
One last video of the F-16's first "unofficial" flight.
I thought we were going for Politically Induced Oscillation. Have had some of THAT lately...
ReplyDeleteA fellow I shouldn't name let me fly with him on a Saturday morning in 1989 or so. We took up a Citabria, and did some spins. I had more fun than is legal that day. He let me take the stick and try to hold a heading. Never done that before. I got into some kind of rolling oscillations pretty quickly. Unfamiliarity with rudder correcting for the prop wash started it. He asked if I was trying to fly like Stevie Wonder.... We both laughed, and I got to try again. This time, my left wing dropped a bit and we were sorta stable. He asked if I walked around with my head resting on my shoulder. Tougher than it looks...
When he took over it was straight and smooth, effortless. We did some bump and runs, then he did a short departure(?). We nearly did a knife edge pass after zooming along the runway and pulled 2 G's. I wasn't ready for how heavy my head was. I did a lot of thinking about our WW1 flyers after that "lesson". I really had a ball. I can see how a Gnome engine would kill you if you were unfamiliar with flying one.
Politically Induced Oscillation....Interesting concept. I'll have to turn it over to our resident political geniuses for further discussion.
ReplyDeleteSounds like you had a fun time. I've mentioned before that there's a guy with a Christen Eagle that flies out of our airport. Regularly does Acro over my place. I should charge him rent, I mean I own the airspace over my property....right? One ride a month, that's a fair price...right?
Ah well, one can dream.
PIO.
ReplyDeleteWhen I first saw the title I thought, "Political Information Officer" and "What the Hell is Tuna up to now?"
Then after reading the post the thought was, "Ah, there's a name for that!" I've seen it in one of my flight sims (IL-2). You want to correct, you really, really want to correct but you know that the best thing is to "STOP CORRECTING DAMN IT!" Sometimes you have to let the aircraft do what it knows how to do, as in fly.
Easy to do in a simulator where there is no worry about dying. Can't imagine that happening in the air, well, I can but I don't want to.
That last clip, the Viper just wants to fly, the unofficial first flight. Wow.
Think what might have happened if he'd ejected or worse.
DeleteI’ve had similar experiences in IL-2 (and X-Wing, Wing Commander, A-10 2, Flight Sim, basically I’ve probably found a way to cause PIO in everything I’ve played...). Probably one of the reasons I prefer fairly precise sim gear that takes a lot of movement to induce a big response in most games.
DeleteOne interesting side effect of this came during my abortive flight training. Particularly during my introduction to slow flight at the back of the power curve, my instructor had to keep telling me to make bigger control inputs, which he also noted was the opposite of what he usually had to tell students.
Yeah the flight simulator in Google Earth has some of those tendencies. There seems to be a problem with the throttle. I keep pulling it back and it pops back to full. (No, I don't touch the throttle up button.) And flight control inputs at 875K are much smaller than at 350K.
DeleteRe: Politically Induced Oscillations.
DeleteI fear we're going through those now. I'm reminded too much of the last few decades of the Roman Republic, where each action induced others, with wild oscillations resulting. Each stretch of the permissible boundaries led to another stretch in a different direction until the boundaries finally snapped. Each attempt to restore order, from Sulla through the 2nd Triumvirate, led to different breakages until finally Octavian finally put it together in a way that only mimicked the forms of the older ways.
It was peace, but at such a price!
DeleteThat F-16 flight was impressive, especially how he actually got to fly under control. Well Done,Sir!
DeleteScott, Yeah, I was half expecting to see an ejection. Without a doubt he had to go change his drawers.
DeleteI'm pretty sure the F-8 guy had to survey both his skivvies and his bag, and earned a new call sign in the process. I wonder if the KAL pilot logged 5 landings? I am reminded of a quote from the early days that I learned from my instructor, “Aviation in itself is not inherently dangerous. But to an even greater degree than the sea, it is terribly unforgiving of any carelessness, incapacity or neglect."
ReplyDeleteI would suspect the KAL Pilot probably logged his LAST landing as a KAL Pilot after that.
DeleteI've heard, and used, that saying several times. Usually in Debriefings....
One of the projects my dad worked on was finding out/setting the max speed at extremely low altitude handling characteristics of the early F-4. PIO resulted in at least one crash, and from what I remember at least one fatality. I remember him saying that the Phantom wasn't designed to fly anywhere close to the ground.
ReplyDeleteYou see PIO involved in a lot of single-car crashes, those that are not actually suicides. Especially on ice or water.
They must have been some improvements in the Flight Controls based on that project. I always thought the Phantom had very good low level characteristics. Very solid feel. The Eagle had so much lift in the wings and fuselage that at low level it got bounced around quite a bit.
DeleteOh yes, cars on slippery surfaces, very similar characteristics, causes and cures.
I've seen film of some terrible Phantom accidents, including a test-pilot fatality as the Phantom Saber-danced down the runway before exploding in a ball of flames. IIRC, pilot attempted to eject, but was out of parameters and was caught in the fireball. I was a kid and remember saying, "Whoa! Neato!" or something like that, and my father came down on me like a ton of bricks. "Someone really brave and a lot more skilled than you'll ever be DIED there!" And so on. I'd had no idea someone died. It was something like Nova, very early on. I felt sick that I was thrilled by that scene, but then, I didn't know what the story was as I'd just came in.
DeleteThere were a lot of aerodynamic improvements made in the mid 60's, from what I've gathered.
DeleteLittle things add up when you're 20' above the ground and going balls to the walls fast.
Larry,
DeleteLater model F-4s mitigated that problem by blowing engine bleed air over the wings. Which worked fine unless you had bleed air duct failure and then you were blowing 1000 degree Celsius air directly over the internal wing tanks. Emergency Procedure for that incident? Land as soon as possible.
(Most Emergency Procedures said Land as soon as conditions permit.)
Beans,
DeleteYep. PK of hitting the ground is only very slightly under 100%.
I suppose that test pilot would've been testing a solution to that problem. Or else something mechanical went wrong that induced it, since he was a test pilot and they had cameras on him.
DeleteThat reminds me of an incident that occurred in the ~1960 period with a flight of F-100s being ferried across the Atlantic to Morocco (or at least, that was their next stop after the Azores). Something failed in the climate control system and it was blowing a lot of exceedingly hot air into the cockpit. After not too long, after some discussion with his flight lead, he tried to jettison his canopy. It failed. He ended up crashing only 20 miles short of the runway. The heat had gotten him, and all his mates could do was try to talk him through procedures as he was getting increasingly incoherent. :(
I suppose heat must come from engine bleed air. I was a passenger in a C-130 going from McChord AFB in Tacoma to Elmendorf AFB in Alaska.
DeleteIn December. Their heat was screwed up, but not so much that it couldn't be turned off. It was full blast or off. So the crew would cycle it. We'd get something out a furnace, start sweating profusely, open up our coats, and then it would be off and just as quickly dropping to well below zero. That was the most miserable flight I've ever been on.
I've read that troops on the ground were happy to get any support from fast movers that they could, but that they weren't real happy with F-4s if it had to be in close. They had a tendency to have a larger CEP than other aircraft. I'm really trying to hard to remember the details, but I can't remember if it was Marines complaining about early Phantoms vs. Skyhawks, or Army complaining about early Phantoms vs. Super Sabers (I still want to spell that Sabres, thanks to two formative years in Canadian (Newfoundland) schools). I think later F-4s, like the E model, would've been most excellent, while with the early models, close air support was a "nice to have" and preceded some important electronics advances, but I don't know. But curious to find out what I can from those who've been able to work in the greatest office in the world. :)
DeleteI was just thinking about willy fuds and carrier landings.
ReplyDeleteNight flight ops stopped as soon as the last aircraft (except one) was recovered.
Yeah, I'm not sure how much training is actually being accomplished at 0200 local time (the time of the accident). I wondered about that.
DeleteThumb and finger. Never flew anything with electric trim but did develop a habit of thumb and finger. My first instructor made me spend hours stalling a Piper J-4 in all kinds of turns, climbing and descending. Hammered in the, "That rudder doesn't turn anything in the air" lesson. Later experiences made me glad he did seeing others making basic mistakes. I can only imagine how much faster and violently military aircraft react.
ReplyDeleteThumb and finger works all the time. Even when maneuvering hard. The rudder works amazingly well in an F-15 at turning it 180 degrees almost instantaneously. If you're pointed straight up, at near zero airspeed and have plenty of altitude below you. Not sure how successful it would be in a multi-bogey furball, but it's very fun in a 1 v 1 dogfight. Unless you're on the receiving end anyways.
DeleteI remember someone writing about flat-plating F-105s and what would result. A very exciting ride above several thousand feet. And then pilots passing it on to newer ones, "Try this to escape, so long as you're above xxxxx'" They'd come back white-faced and shaking, but would pass it along to the next bunch. But I guess things were different in the 1960-ish era.
DeleteI've read that also. I can't remember where though.
DeleteThinking about it more, I think it was Ed Rasimus, in "When Thunder Rolled". Not 100% sure, though.
DeleteThat was Ed. I remember it well.
DeleteA very good post, juvat. I previously had only a small amount of knowledge on that subject, now I have a greater fund of knowledge on PIO.
ReplyDeleteThanks for the post.
Paul L. Quandt
Well, here's hoping you don't get it demonstrated on a future airline trip.
ReplyDeleteOh yeah, that's the bane of a pilot's life, especially on a carrier approach going through the burble... And that FedEx crash at Narita that killed the crew was PIO too.
ReplyDeleteYeah, I can imagine you'd have to be very careful on the controls there. Slow and trying to maintain a glide path then hitting a bit of turbulence. The urge to jerk the controls would be hard to resist.
DeleteFly-by-wire systems have faults all their own. F-22 and Saab JAS-39 Gripen both did pretty much the same thing, more than once, IIRC, before they got the flight control software tuned.
ReplyDeleteEr, so did many of Airbus' planes. In normal aircraft it was 'trust your instruments,' but in early Airbus computer-controlled cockpits it was 'verify your instruments.' Too many losses labeled as 'pilot error' may actually be 'computer error.'
DeleteLarry,
DeleteOne of the reasons I chose the Eagle (or was glad I got chosen for it) was exactly that. In the Lawn Dart, the pilot gets a vote, the computer says yes or no. In the Eagle, the pilot say go, the computer makes it happen.
Beans,
DeleteWasn't that the cause of the crash of Air France off the coast of Africa?
Beans, Juvat -- There used to be three schools of thought. One was that the pilot was in charge and the systems on the airplane were there to support the pilot. The other extreme was that the airplane knew better than the pilot and the pilot was only there to support the airplane. There was a school of thought that was in the middle of that.
DeleteFor years Boeing was in the first. Airbus has always been in the third. McDonnell-Douglas was in the middle. Most of the Airbus accidents have been related to the inability of the pilot to get the airplane out of the hole it has gotten itself into because that is software. The Toulouse airshow accident was that. The lose of the Airbus in the Mid-Atlantic a few years ago was that. Now Boeing has maybe joined Airbus based on the 737 Max accident in Indonesia. As a former C-130E/H pilot, I just can't imagine seceding control to a bunch of computers; they can help me but they damned well better do what I tell them to do, especially if you are flying on the edge of the envelope.
" I learned that at Luke after I swapped ends trying to tree my IP in a 1 v 1. (He starts going straight up. You start to chase him. One or the other of you is going to run out of airspeed. That one dies.)"
ReplyDeleteBut, but, the Eagle will accelerate going straight up until it leaves the atmosphere, or so I've always been told. Someone was pulling my leg ?
I remember in Air Force Undergraduate Pilot Training, when I got to T-38s the emphasis that was given to avoiding PIOs. There wasn't anything that I remember about that from the T-37 portion of the training.
ReplyDeleteAs to how to hold the control stick, when I started to learn to fly at the tender age of 14, the instructor took me out in a Piper Super Cub for stick and rudder familiarization prior to flying the sailplane trainer. He told me to grab hold of the stick in a particular manner which I won't fully describe. I got a good tight hold on the grip with my whole hand when what he actually wanted me to do was to take it with my thumb and a couple of fingers. That caused me to harshly control the airplane. He had to correct me before the next Cub flight. I soloed in a Schweitzer 2-23 when I was about 14 1/2 years old. You had to have good judgement in the pattern as there was no going-around. It was great fun.
That was a Schwizer and not Schwitzer. And it was a 2-22 not 2-23 (which I flew a few years later).
Delete