Inappropriate comments about RJ crash?

[AAflyer]

From a previous employers' CRJ flight manual

iv. PTCH- Pitch mode will allow the aircraft to climb at a set pitch attitude. The best pitch attitude usually falls around 2.5 to 3 degrees nose up. This mode allows for a smooth transiition from intermediate level off climb by simply sellecting the proper nose up pitch. There is also some "built in" stall protection because at 3 degrees nose up the aircraft will not stall, it will simply stop climbing. When using this mode, pitch selections using the control wheel must be done slowly, one at a time. Moving the wheel faster than this will cause passenger discomfort

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Thoughts.....???

Holy Cow,

You are going to stall more aircraft out of altitude if you think this correct. Any aircraft can stall at any airspeed and any pitch angle. Good Grief, this is basic stuff guys.

AA

 

[PCL_128]

You guys are fixing to get yourselves hurt.

That's for sure.

 

[Rook]

Don't want to condone the actions of my departed co-workers but they did recover from the unusual attitude they were in. I think we should look more at G.E. and the core-lock phenom. The 410 issue has been addressed and re-addressed enough. I just want to have more faith in the CF-34 when flying around TRW's, Heavy rain, strong turbulence, etc. with the possibility of flameout. Comair flamed one out after a lightning strike and were able to get it re-lit. Anyone have any details on that incident?

Rook

 

[rtmcfi]

Of course, my above statement assumes you have enough thrust to maintain airspeed. I think Surplus mentioned this earlier. If you had drastically reduced power for some reason, you won't maintain the altitude you had achieved. As you slow down, due to the reduced thrust, you lose lift, and you will descend. Let's say you don't change your pitch at all. As you start decending, you introduce a vertical component of wind. The faster you sink, the more vertical wind you get. As you slow down, the less horizontal wind you get. Your resultant wind will give you a greater AOA. At three degrees pitchup, does your resultant relative wind exceed the critical AOA? I dunno. Quite likely. However, if you do not exceed the critical AOA, you will not stall, but you are still going to decend untill lift=weight.
In any case, refer to the QRH!

 

[rtmcfi]

Holy Cow,

Any aircraft can stall at any airspeed and any pitch angle. Good Grief, this is basic stuff guys.

You are absolutly correct. I am in no way trying to say it won't. By the same token any wing can create lift at any airspeed greater than zero, and at any pitch angle. I was trying (rather poorly evidently!) to explain relative wind, and what makes it up.

In the example of bringing both engines to idle at 3 degrees pitchup, you may not ever stall, but you will hit the ground. And please keep in mind that I am not saying you won't stall. Without trying it, I really don't know. (I think it will stall, as you are quickly gonna run out of forward speed, reducing your horizontal component of wind, and as you start decending, relative wind is going to change rather quickly to a big angle.) What I am saying is you will only stall if you exceed the critical angle of attack.

 

[Wasted]

What I am saying is you will only stall if you exceed the critical angle of attack.

That's good. If I were you, I'd shut up and leave it at that. You came in here saying some scary things and then qualified it, and then came back again and said some more scary things, I would quit while I'm ahead if I were you. This entire exchange has probably left you a little questionable in many reader's minds, but I'm hoping it is merely poor communication skills.

 

[AAflyer]

You are absolutly correct. I am in no way trying to say it won't. By the same token any wing can fly at any airspeed and pitch angle. I was trying (rather poorly evidently!) to explain relative wind, and what makes it up.

In the example of bringing both engines to idle at 3 degrees pitchup, you may not ever stall, but you will hit the ground. And please keep in mind that I am not saying you won't stall. Without trying it, I really don't know. (I think it will stall, as you are quickly gonna run out of forward speed, reducing your horizontal component of wind, and as you start decending, relative wind is going to change rather quickly to a big angle.) What I am saying is you will only stall if you exceed the critical angle of attack.

Glad you quantified your statement, not sure to whom you are explaining relative wind too? I hope once again if you have reached this level of the game you understand AOA, Relative Wind, and how and when an aircraft CAN stall. Unfortunately there are probably some that do not.

Cheers,
AA

 

[rtmcfi]

Well, perhaps they are finding me a little questionable. For that I am sorry. Perhaps they have a better idea of relative wind. Perhaps they will research relative wind a little bit. I am not so sure I said anything "scary", unless one does not understand aerodynamics themselves. In that case, what you don't understand can be intimidating, or baffling. As a captain, shouldn't you be a little more helpfull? Do you tell your FO's to shut up? You might want to listen to them. You may find they have a better, more thorough understanding of something than you. You may find they are weak in an area, and you can explain it to them. Or you can tell them to shut up. It is evident that there are people who read this board that do not have a good grasp on even basic aerodynamics. I am attempting to get people to think critically about it. And now I will shut up about it, cause this thread is drifting!!

 

[Wasted]

Just thought I'd help you keep yourself from looking like an idiot, that's all. Have a nice day.

 

[Rogue5]

By the same token any wing can fly at any airspeed and pitch angle.

Incorrect.

It is evident that there are people who read this board that do not have a good grasp on even basic aerodynamics.

Correct...

 

[PCL_128]

Incorrect.



Correct...

Classic.

 

[KeroseneSnorter]

Don't want to condone the actions of my departed co-workers but they did recover from the unusual attitude they were in. I think we should look more at G.E. and the core-lock phenom. The 410 issue has been addressed and re-addressed enough. I just want to have more faith in the CF-34 when flying around TRW's, Heavy rain, strong turbulence, etc. with the possibility of flameout. Comair flamed one out after a lightning strike and were able to get it re-lit. Anyone have any details on that incident?

Rook

You can turn any jet engine into a solid block of metal of you abuse it enough.

As I understand it, the NTSB said the first one cooked at the time of initial flameout. Understandable in a departure from controlled flight at full power, shut the air off with all that fuel running through it and bad things can happen quick.

The second engine not relighting appears to be operator error (according to the prelim. from the NTSB) since they never got the airspeed up to the airstart envelope.

Just an opinion from reading the report, Have to wait for the final.

 

[say again]

Just thought I'd help you keep yourself from looking like an idiot, that's all. Have a nice day.

You tried wasted, but I guess he just doesn't get it!!!

 

[say again]

Deleted

 

[surplus1]

rtmcfi,You're not completely in left field but the way you articulate it creates some doubt.

I recommend that you not climb to the top of the envelope in pitch mode expecting that the airplane will just descend when you run out of power.

It's true that it will descend but it is also true that it will more than likely do so as the result of the stall. Even if you don't actually stall the wing completely (aerodynamic stall), you will activate the shaker and the pusher as the SPS takes over to prevent the impending aerodynamic stall.

As you get closer to that point, the auto pilot will be trimming nose up slowly in the attempt to hold your commanded pitch attitude as the power available deteriorates. (If the aircraft has no "trim wheel" it's not so easy to observe this) By the time the pusher activates, the elevator will be trimmed close to full nose up, if its not already there.

After the pusher releases during the first descent, the nose will pitch up again due to the higher airspeed achieved during the push over and the out of trim condition (full nose up). This will probably result in a second activation of the shaker and pusher. You'll wind up "fighting the pusher" - always just a tad behind. In other words, an upset followed by a series of secondary "near stalls". Get too far out of synch and the consequence will most likely be a full aerodynamic stall of the wing.

If the airplane you happen to be flying is a CRJ that will almost guarantee a double flameout. That's becaise the engine installation of that aircraft puts the inlet in the path of the shock wave (interrupted airflow) from the aerodynamic stall of the wing. No air, no combustion = flameout.

In the CRJ design, the function of the pusher at high altitude isn't really to prevent the stall, its to protect the airflow to the engines. The stall itself is rather benign at high altitudes on that particular wing.

On the other hand, at low altitudes the stall is not benign and could result in a breaj/roll of near 90 degrees. At low altitude the SPS (stall prevention system) is there to protect against that violent stall. You probably don't need to know that minutiae, but you do need to know that at high altitudes it is imperative that you monitor the aircraft closely and do something immediately to correct any approach to a stall, well before you get the pusher. In other words, descend NOW. The descent is necessary because you just don't have enough excess power (if any) and it is not possible to "power out" of the near stall condition.

If you get the shaker at high altitude there's only one solution = descend immediately. You don't have to be at FL410 to experience this. It can happen at any altitude in the 30's with the right weight and ISA conditions.

I have no idea who wrote that piece that Rez O Lewshun posted, but I would urgently recommend that you not follow that thought process.

The statement he posted includes this: "There is also some "built in" stall protection because at 3 degrees nose up the aircraft will not stall, it will simply stop climbing." I disagree completely. One big bump or a little inattention could ruin your whole day.

At high altitudes, particularly near the extremes of the flight envelope for your weight and ISA, that is not a factual statement.If you believe that you could be in for a world of hurt.
.

 

[Guitar Guy]

That's becaise the engine installation of that aircraft puts the inlet in the path of the shock wave (interrupted airflow) from the aerodynamic stall of the wing. No air, no combustion = flameout.

Do you mean "disturbed subsonic flow" or maybe "wake" instead of "shock wave"? I don't think you'd have a shock wave during a deceleration to a stall even at high altitude. But I don't fly the CRJ, so I thought I'd ask.

 

[U of I Tweak]

Not necesarily. A plane is parked on the ramp, facing directly into a 20 kt headwind. Now the wind kicks up to 100 kts. Has the relative wind changed? Has the AOA changed? I'm not trying to be a smart a$$, just trying to work through this....

I think the big argument with your example is that you're talking about an airplane on the ground. The weight of the airplane is supported by landing gear, not the wings, so aerodynamics are irrelevant.

 

[Rez O. Lewshun]

I have no idea who wrote that piece that Rez O Lewshun posted, but I would urgently recommend that you not follow that thought process.

The statement he posted includes this: "There is also some "built in" stall protection because at 3 degrees nose up the aircraft will not stall, it will simply stop climbing." I disagree completely. One big bump or a little inattention could ruin your whole day.

This comes from the flight standards manual for a CRJ operator, FAA approved. It also describes use of VS and IAS/DES/CLB. Any of the three, PTCH, IAS and VS can be used safely if the limitations of the aircraft, flight profiles and flight (dispatch) release is followed.

As far as the AOA/ pitch attitude, I wasn't seeing things the way I should've. I climbed inside my head and into the books and I'm on the right path. To those that contributed positively...thanks.

All I want for Christmas is an AOA indicator.

 

[:-)]

All I want for Christmas is an AOA indicator.

Why?

Is an AOA indicator harder to ignore than an airspeed indicator?

Seriously, if some pilots are willing to ignore minimum climb speeds, what makes you thing that they would honor AOA?

Edit to add more. The reason given by most CRJ pilots for not climbing in A/S mode is that the airplane chases speed. It follows that they are allowing A/S to vary instead of climb rate. How will an AOA indicator help those pilots?

Calvin

 

[surplus1]

Do you mean "disturbed subsonic flow" or maybe "wake" instead of "shock wave"? I don't think you'd have a shock wave during a deceleration to a stall even at high altitude. But I don't fly the CRJ, so I thought I'd ask.

Good call!I do mean "disturbed subsonic flow" -- not the shock wave associated with high mach or "near sonic" flight. According to the manufacturer of the CRJ airframe, when the boundary layer separates in an aerodynamic stall of the wing, the disrupted airflow is directed towards the engine inlet and can reduce the inlet airflow to a level lower than required to sustain combustion (when at or near the limits of the envelope). [This is not due to the wing design itself; it is due to the placement of the engines with relation to the wing]. As a result, airflow distruption on the wing at high Alpha, is sufficient to potentially cause flameout. [I tried to state that as carefully as possible -- I hope it's intelligible]. Again, according to the manufacturer (and they have the test data), the settings of the SPS are designed to activate the shaker/pusher at a point that will avoid this phenomenon; thus preventing flameout.

The CF-34 engine that powers the CRJ is, by comparison, a small engine and doesn't have a big inlet to begin with. The by-pass ratio is relatively high for engines of that size. Additionally, the internal protection against external damage from a catastrophic failure also serves to restrict airflow to the engine core. I wouldn't go as far as to say that the engine is "prone" to airflow interruption, but I would say that it is somewhat "touchy" compared to other engines, due to all of these factors. As a consequence, pilots need to be careful about operations that contribute to airflow interference. We don't have to be "worried" about it but it is necessary to be prudent and avoid doing "unusual" things, especially at the extremes of the performance envelope. In heavier air an well within the envelope, operation is quite "normal".

Personally, I don't find this unique to the CRJ design. Every engine/airframe combination has its own "quirks" if you will. In my own experience all airplanes require careful attention when operated at the extremes of their performance envelopes; not just CRJ's.

If you choose to operate outside of the envelope, it is safe to say that you can expect the unexpected.

In my humble opinion, all of the critical knowledge we have should be provided to flight crews in the course of their training. I don't think manufacturers should be keeping little "secrets" from operators and I don't think operators should be limiting flight crews to the "bare minimums". Obviously there are limits; we're not engineers and we don't need to know how to build the airplane, but we do need enough information to not become unknowing test pilots.

Please don't take that as a veiled bashing of PCL for it is not so intended. In my opinion, none of the operators (including my own airline) are providing enough information. In some cases that is because the operator's training cadre does not have the information itself. For that I blame both the manufacturer and the FAA, not the airline.

As an example, during the Public Hearing associated with the PCL accident, I listed to the manufacturer's chief traing captain insist, over and over again, that it is OK to train stall recovery at 10,000 ft because the techniquie is "identical" regardless of altitude (his words). At the risk of being called an idiot myself, that is unadulterated bu11sh_it! The recovery from an approach to stall at 10,000 feet is NOT the same as the technique required at FL410. In fact it's not even close.

That few operators teach pilots the differences is no secret; they don't. That's because we spend hours tooling around in simulators "practicing" canned approaches to stalls that apply to Cessnas, not high performance swept-wing aircraft and virtually no time even demonstrating what happens at very high altitudes. Pilots need to know what to expect at lower altitudes AND at extreme altitudes, particularly the latter. Stall recovery is NOT the same when you have no excess power as it is when you have lots of excess power.

At low altitudes the objective is to protect against altitude loss. At high altitude it is the exact opposite; give up altitude and get the wing flying again.

The idea of "practicing stalls" with a certain pitch attitude, a particular bank angle and the concept that losing 100 ft of altitude is a check ride "bust" is pure nonsense and a waste of time. Any "stall" that occurs in an airliner is going to be inadvertent and a surprise to the flight crew. Pilots don't stall airliners intentionally no matter how "cowboy" they might be. Training needs to be realistic; not an excercise in checking off squares to please some FAA inspector who often has minimum knowledge, if any, about the particular airplane.

I could rant forever about that but I've already said too much. So, I'll end this by saying: the training is inadequate. That's not a PCL problem, it's an industry wide problem, and by that I do NOT mean "regional" airlines only. Adequacy of training is an exception; it ought to be the rule.