Pitch controls airspeed?

[AJ]

I was reviewing this thread for old times sake and see that MCM never really answered 3WE's comments about the Pinnacle CRJ thread.

Are you kidding? The responses have been extremely informative!

[MCM]

What specifically didn't I address?

I thought I had covered it off pretty well.

[Praehapt Bubtah]

I was reviewing this thread for old times sake and see that MCM never really answered 3WE's comments about the Pinnacle CRJ thread.

[MCM]

Yeah, having "fun" with an aircraft can be ok, depending on how you do it.

Letting speed build up and then doing 6000fpm is not inappropriate if it is handled correctly, and it can be a perfectly smooth manoeuvre. It is something that is also done for operational reasons... in fact I usually end up doing it every second day of flying due to a particular SID design.

They did not to do that.. they pulled up so hard that they hit, what was it... about 2.8g, and triggered the stall warning. That is irresponsible in an aircraft of that size. So too is stamping on the rudders to "wiggle" the tail. The aircraft is NOT designed for that sort of behaviour. Sure, it is strong enough to resist it (most of the time), but it is not the intent of the aircraft and so you shouldn't be doing it. The deflection they got it up to was really quite high.

So there is "responsible" fun, and irresponsible fun.

[3WE]

Thanks for your coments MCM.

One other thing I have said about this crash. I really do not blame the pilots for having a little fun.

A "race to FL410" is not all that bad of a "game". The skill to nail a maximum rate of climb airspeed....working with ATC to see how the cards will fall, can you get there faster than anyone else in the company....and getting a plane to 410 where apparently it may not have the power to "get there well" is an interesting challenge.

Amazingly enough, Barry Schiff in an AOPA pilot magaizine once mentioned getting a block altitude in passenger-loaded L-1011, letting the speed build and then achieving a 6000 fpm climb. I have to believe he did this with high levels of gentleness- I am sure it takes VERY little to get a plane load of passengers upset.

So, "having a little fun" with the plane is not a problem. (I'm not so sure that negative G's are ok- that could really mess up a galley! As seen on Airplane, spilling all the coffee is a TOTAL air disaster, and a time to panic!). Don't get me wrong- I know the plane can take negative G's, but it does seem like a magical line you shouldn't delibarately cross when it ain't your airplane! Trying to see how fast you can climb (gently), and some rudder waggle- no foul....

Anyway, I'll TRY to shut up....even though, yes after they lost power, they were most incompetent in restart procedures, and overflew a couple of suitable landing fields (although I don't know that the weather was suitable for a power-off landing in their "defense").

Gabe and I have a little debate going on the flapless DC-9 crashes- In those cases I have a little bit of forgiveness for the pilots pulling up too much. He has somewhat less forgivenes- although we see each others point.

[Gabriel]

I am an avid supporter of pilots not being blamed (for obvious reasons ), with "pilot error" usually being a cop-out to not go into the background in sufficient detail

I agree. Human error can be a link in the chain of events that lead to an accident, but it can never be a root cause.

A root cause always need a corrective action. What's the corrective action for human error? To tell the human not to err? That wont work. Humans make mistakes period. The only way would be to get rid of the human at once, and that's not possible and will never be (some human will have to design the engineer-less software that will design the pilot-less plane).

The design (of the airplane, of the procedure) should be fairly design proof. It's not? Then it's a design problem, not a pilot error.

The training should be such that pilots will not make so many severe mistakes in a row to overwhelm the mistake-proof design. It is not? Training problem.

The culture should be such that only adherence to the procedures and playing on the safe side is acceptable. It is not? Culture problem.

Pilot selection and continuous evaluation should be such that those that just aren't good or willing enough to deal with the task are kept away from flying. It is not? Recruitment and flight department problem.

You can't blame a bad pilot for being bad.

Now, what about a good pilot that is well trained within a good culture and passes always with A grades, but then just decides to do stupid things that he knows are stupid and officially unacceptable?

That for me is not an "error" or "mistake". It's willful misbehaviour, and many times criminal negligence. You CAN blame a pilot for that.

One saving grace is that I firmly believe that had the flight had passengers on board, it would never have happened, as the crew only took the actions that they did because it was just them.

I agree with that: They would have not pulled high and below Gs during the climb, and they would have not deviated from their filled flight plan to play the 410 club. BUT... what if...

They were once flying at 370 and were asked by ATC to climb to 410?
Or they encountered a widshear that makes the stickshaker go off?
Or had a Colgan-like stickshaker during the approach?
Would they have been up to the stack?
I'm not so confident.

[MCM]

3WE,

I started to write an explaination of some of the issues surrounding these types of crashes... but this is one of those accidents that just leaves you amazed.

I am an avid supporter of pilots not being blamed (for obvious reasons ), with "pilot error" usually being a cop-out to not go into the background in sufficient detail.

On this occasion, however, what can you say.
The contributing factors -

- The culture of the airline was probably one. (I can go into more detail if you need it, but I think you probably understand the concept of the culture making a decision have a certain bias behind it).

- The fact in normal service the crew had quite possibly not operated the aircraft in a performance - limited way, and so were not as familiar as they should have been with the issues surrounding speed and climb to limiting altitudes.

The way they flew the aircraft prior to even climbing to FL410 is "interesting", and shows the state of mind... they had an empty aircraft, and they were going to have fun with it. Quite large RUDDER deflections, high positive (and below 1) g manoeuvres... they were out to have fun. They had a stick shaker activation early in the flight, and it didn't "put the wind up them" sufficiently to stop them doing it again. State of mind.

Why did they stay at FL410 when they realised that they couldn't maintain it? Good question, however based on the other decisions they had made during the flight I can't see why you could expect them to start making the correct decisions then. They "should" have just started a descent, and why they didn't... I can only put down to inadequate training, and the current state of mind.

They continued to make questionable decisions and take poor courses of action right until the crash.

All you can do is investigate why the crew felt that treating the aircraft in that manner was appropriate. My guess is that the "culture" of the airline lead to it.

One saving grace is that I firmly believe that had the flight had passengers on board, it would never have happened, as the crew only took the actions that they did because it was just them.

[Gabriel]

Wow, I never thought of this. I read that stalls happen when you fly too slow. And given that you slow down to land, if you turned into a tailwind, I see that you would lose airspeed and might stall. YIKES

Exactly what book are you reading to learn to fly?

Anyway, drop it and read this one. It's freely available on-line and by far the best resource I've found so far (and the only one written for pilots that has no important conceptual errors):

See how it flies

That is, if you really want to understand how all this stuff work.

[Praehapt Bubtah]

"You must be careful when turning to downwind because the airspeed will go down as the plane catches-up the wind"

Wow, I never thought of this. I read that stalls happen when you fly too slow. And given that you slow down to land, if you turned into a tailwind, I see that you would lose airspeed and might stall. YIKES

[3WE]

Originally Posted by 3WE
So they are sitting there, at a great stall attitude, and watching their airspeed decay AND ARE OBVIOUSLY AWARE OF IT.

Then the stick shaker goes off.

Then the stick pusher goes off.

Then they override it by over-pulling-up the stick pusher.

Then the stick pusher goes off a second time.

Then they override it by over-pulling-up the stick pusher again.

Then the stick pusher goes off a third time.

Then they override it by over-pulling-up the stick pusher again.

Then the stick pusher goes off a 4th time.

Then they override it by over-pulling-up the stick pusher again.

But they let the aircraft stall. [end Gabe's modifications of 3WE's rant]

Fixed

1. All previous 3WE rants X 100,000 Why/How in the hell do you stall a plane when the attitude and airspeed is "screaming" imminent stall and the stall horn and the stick shaker is "screaming imminent" stall and you have 39,000 feet of excess altitude, and you are sitting there talking about your attitude and decaying airspeed, rant rant rant rant rant rant rant. (sorry, but geez!).

2. They didn't know that airplanes with tail-mounted engines tend to flame out when stalled???????

3. They did not have ATC clearance to descend, and if they had descended without clearance, ATC could ask for written explanations, thus calling attention to the fact that they were flying in an unprofessional manner, and then they lose their jobs??????

4. They were they hoping and praying that against all odds, that MAYBE....MAYBE it would hang on and not stall????

5. OR....were they simply idiots.

6. I suppose all of the above or any number of combinations of above are valid reasons too.

Sorry..... MCM if you have any thoughts that Gabe or I missed, I would be interested in hearing them.

[Gabriel]

MCM,

First, I don't disagree with you saying that, from a practical POV, in the final approach you use thrust for speed and pitch for altitude.

I've said it from post 1. I agree 100% with you that your explanation is correct. What I've said is the "thrust controls altitude and pitch elevator controls airspeed" is just another way of explaining the same thing.

No matter what explanation you use, and no matter if it's in a 747 or a C-152, in each case there is only ONE combination of elevator and throttle input that will take you from speed A to speed B while keeping the same descent slope, and only ONE combination that will take you from descent slope A to descent slope B while keeping the same speed.

None of "elevator = speed, throttle = altitude" and "elevator = altitude, throttle = speed" is an absolute truth, but rather "tools" to help explain some things in different ways.

The closest to the reality (but not exactly THE reality) is that elevator controls AoA and throttles control power/thrust.

In any case, a change in only speed, only vertical speed, or both, all require a coordinated use of elevator and thrust. And IMNSHO the pilots, at any level, should understand not only what combination works in each case but how and why. And I'm sorry but, while I'm sure you and most do, I have the strong feeling that more than I wanted to don't. These are quotes from instructors or very experienced pilots, said to me (and 3we knows about one of these):

"The Tomahawk doesn't have so nice handling characteristics to fly with a tailwind because of it's T tail"

"The Cessnas are more stable than the Pipers because of the high wing, where the weight hangs from the lift"

"You must be careful when turning to downwind because the airspeed will go down as the plane catches-up the wind"

(With me in the right seat of the Grumman Tiger and, seeing we were way high and fast during final approach with a clean wing, asked if he wanted me to drop some flaps) "No, the flaps on this plane are very effective, they increase the lift a lot, which will make things worse" (He also rejected my suggestion to go-around, we stopped in the stopway of a 3000+ ft runway)

I know there were many more, but these are the ones that come off the head now.

About Austral (not Air Austral), I'm not questioning that it's hard to recognize which instrument is failing, and that then it's not that easy to hold altitude and speed based on pitch and thrust. BUT PLANES STALL AT AN AoA, AND AN AIRPLANE THAT IS FLYING STRIGHT AND LEVEL WITH 2deg ANU IS NOT ANYWHERE REMOTELY CLOSE TO STALL, and yes, I expect a professional crew to notice that before extending the slats at cruise. The CVR showed that they were not trying to determine what instrument was the wrong one, they just said "speed down, increase thrust, still down, ask for lower, they said hold on, no matter, go down anyway, speed still going down, about to stall, pumps and slats, oh shit".

Again, I don't criticize them for not flying thrust and pitch, not even for not being quick enough to recognize the airspeed failure, but for calling a stall when ALL CUES, with the only exception of airspeed, were that the plane was nowhere close to stall (2deg ANU, altitude steady, VS steady, no buffet, no stick shaker, no mushy control forces, the plane flying perfectly normal and behaving perfectly normal and reacting perfectly normal to all the pilot inputs, except IAS)

No, I have not flown in real IMC and have no instrument rating, so I might be forgiven those mistakes, which I doubt I would have made anyway (on the other hand, I would have probably been a victim of spatial disorientation and ended in a graveyard spiral 178 seconds after entering IMC)

[Gabriel]

So they are sitting there, at a great stall attitude, and watching their airspeed decay AND ARE OBVIOUSLY AWARE OF IT.

Then the stick shaker goes off.

Then the stick pusher goes off.

Then they override it by over-pulling-up the stick pusher.

Then the stick pusher goes off a second time.

Then they override it by over-pulling-up the stick pusher again.

Then the stick pusher goes off a third time.

Then they override it by over-pulling-up the stick pusher again.

Then the stick pusher goes off a 4th time.

Then they override it by over-pulling-up the stick pusher again.

But they let the aircraft stall.

Fixed.

[3WE]

FAO MCM, Pinnacle CRJ

Apolgies to Prahehapt, but I'd like to hit MCM with a brief hijack subject.

Gabe and I talk a lot about stalling and think it's something you should not do, at least not do inadvertently and not do it in an airliner with tail-mounted engines for which a stall is not an approved maneuver.

Gabe will tell you that I get livid when the Pinnacle CRJ crash is discussed.

I mean, "holy crap", you are flying at about 20 degrees ANU and 16 to 17 degrees AOA is always cited as the critiacal stall AOA. (yeah attitude does not equal AOA, except for a normal plane in level flight, it's kinda sorta somewhat similar!)

So they are sitting there, at a great stall attitude, and watching their airspeed decay AND ARE OBVIOUSLY AWARE OF IT.

Then the stick shaker goes off.

But they let the aircraft stall.

WHAT IN THE HELL WERE THEY THINKING? (I know none of us REALLY know, but the behavior still strikes me as nearly incomprehensible- except that it's exactly what happened!!!!)

On another board a pilot (well, actually it was ITS) jumped down someone's throat for suggesting that stalls were dangerous.... Well, in a 172, a properly executed practice stall isn't particularly dangerous nor is a full-stall landing in the same aircraft.

But the CRJ flamed out! The dudes knew the nose was sky high, they knew airspeed was decaying and they knew a stall was imminent.

Dang, it sure seems to me that they should have lowered the nose.

I know they didn't exactly have ATC clearance, but there's this rule called "fly the plane first", and another rule that you can deviate from ATC "orders" to the extent needed to address or avoid an emergency.

I guess a dual engine flameout caused by disrupted airflow from a stalled wing where the engines hit the wing wake is awfully dang close to an emergency.

Anyway- if you have further insight on the Pinnacle deal (and defense of the pilots), (or more correctly an explanation of their misunderstanding), I'd love to hear it.

Apolgies for my 487th rant on this subject, and thanks.

[MCM]

The comment you have quoted last was regarding age 11... not in general .

I'll try and go through one by one . I don't disagree with much of what you say, but it is unrealistic in some situations.

Air Austral. Have you flown in IMC or have an instrument rating? If you do, then I'm sure you'd understand just how extremely difficult it is to detect erronious information. What you say about the increasing airspeed, and the thrust vs attitude is accurate, and is of course the way you fly with an airspeed failure. The manufacturers these days are nice enough to give you a table on the correct attitudes for the correct thrusts.

The problem is recognising the failure early enough. Is it the airspeed indicator that has failed? Or is it the Attitude indicator? That is where the problem lies. They didn't know which instrument to trust. Should they have picked it up earlier? Probably. But their reactions show that they did not detect that the airspeed indicator was incorrect.

The other catch in a large aircraft is the amazing difference in performance for just 1 degree pitch change. That 1 degree can very quickly add or reduce speed... far more than the same change in a light aircraft. Flying without an ASI, whist good in theory, is not an easy task, but it is one that crews ARE trained for. And yes, they DO understand the reasons behind it, and the concepts and interrelatonships of pitch and thrust.

Pinnacle CRJ. I'm sure the pilot understood the relationships as well. The problem here is usually one of automation systems understanding... what the aircraft will do in certain modes. He should have known that it was not a clever mode to be using in that situation... and that is definately a training issue.

We're going to have to disagree on the concept of speed on thrust and speed on pitch. For me, the glideslope scenario is the best example of speed on thrust you can get. The aircraft was pitching for a path, and the lack of thrust meant the airspeed decayed to the point of stall.

The problem here is theory vs practice. You can understand the theory of WHY the aircraft is about to stall all you want (and I'd say 99% of pilots do). The problem is then being able to recognise, and take the appropriate action, immediately. That is not so simple, and it doesn't matter how much you know, you're still in difficulty. The pilots on the G/S one knew they were pitching up, and when the thrust came on pushed full forward. The aircraft kept pitching up, and it would have been a matter of seconds until it stalled. That is not enough time to recognise that the thrust is making the situation worse and you are not strong enough to prevent the pitch up and to remove it... something that they would have done if they were given more altitude.

[Gabriel]

Good post MCM,

For me (and I want to highlight FOR ME) it always worked better to understand the concepts first and polish the skills after. And I mean not only in flying but in everything. And yes, I'm the "geek with scientific curiosity" type, and have been so since as far as I can remember (more or less like http://www.youtube.com/watch?v=CmYDgncMhXw)

On the other hand, it looks to me that more often that what I would like to (probably, or I hope, still a small fraction), pilots get to fly big airliners without ever really understanding all these concepts that involve how and why things are what they are.

The worst aviation accident in Argentina (ok, the plane actually went down in Uruguay) was Austral 2553, a DC-9 with frozen pitots.

They missed the wrong airspeed indication, which was getting lower and lower, so they first added power, indicated airspeed kept going down (the real airspeed increased), then they started a descent in an attempt to trade altitude for speed, the indicated airspeed kept coming down (the real airspeed kept increasing), then they feared they were too slow and about to stall, and extended the slats at a speed that was well beyond the slats envelope, one slat segment detached from the wing and that was it.

As the details of the investigation were becoming public I remember I thought "What the f**k? Didn't these pilots understand a sh*t about what keep them flying? Didn't they know that stall is a matter of AoA and not speed, and hence if they are 2 deg ANU and the vertical speed is zero or a small number then the AoA is 2 deg, and hence that they are nowhere close to a stall, no matter if 100 airspeed indicators tell that you are slow?"

The MD-80 no flaps/slats take-off accidents at Detroit and Madrid:
Let's leave out the reasons why the crew did not set and check the flaps and why the TOWS didn't sound (which are certainly the most important part). Why didn't they manage to complete a take-off, something the plane would have been able to do and, specially in the Madrid case, would have not been something difficult to accomplish IMHO (or not so H)?

The Colgan pilot?

The Pinnacle CRJ? I mean, seriously, leave out their childish attitude of using the plane as their toy, not following procedures, lying to the ATC, etc... and let's focus on the knowledge linked to their flight skills. Climbing to the service ceiling in vet speed mode? Letting the speed go below that of best climb and keep climbing an the same vert speed? Let ti fly at a huge AoA, let the stick shaker shake, let the stick pusher push, and not push down to prevent or recover from the stall? I want an ultralight flight simulator pilot to know this stuff!

The case of the 737 of my previous post. You've said:

A great example of speed on thrust. The aircraft path was linked tightly to the elevators, and they followed that path religously. The airspeed decayed due to the thrust being low

Yes, that would be one explanation, but another explanation OF THE SAME PHENOMEN could be "the airspeed decayed because the A/P pulled up". Had the only input been to take the thrust to idle, the plane would have increased its descent rate and not stalled (even not lost a single knot of speed in the long term).

But not, the A/P kept trimming up nearly to the stall. When they changed the thrust from idle to full, the arm of the thrust vector below the CG gave enough additional trim-up effect to keep the plane pitching up and stall despite the full down elevator input, which was not effective enough at that too slow speed. What the crew didn't realize in time was that the plane, even with elevators full down, was trimmed for a too low airspeed and no amount of thrust, not even 10 times what is available in the 737, would make it speed up, that the only way was to nose down, and since the elevator was already fully down the only way was to trim down the stabilizer, and if that was not enough then REDUCE thrust (yes, to INCREASE airspeed). They were lucky that during the post-stall fall the airspeed increased enough for the elevators to gain enough authority, and that they had enough altitude to recover.

The fate of a flight, even after some problems aroused and some mistakes are made, should not depend on luck if there is a viable way to reliably fly out of the problem. And while I know this is impossible to achieve 100%, as much as possible the "luck" factor should not be "what pilot happened to be assigned to my flight today".

I, and I fancy the vast majority of airline pilots, would not have been either interested or capable of learning it...

I believe you, and that worries me...