Humbling sim experience
 

Had an interesting sim session today,

As a result of several high profile loss of control accidents recently my company introduced a special LOC sim session. Interesting training with a lot of background. My particular sim session was done with an ex air force guy. Lot of insight about recovering techniques! In my earlier years I did some acrobatics but no formal training and since then all my flying has been airline type. Aside from the occasional upset recovery during TQ's and occasional type recurrents not much experience in this regime.

One scenario in particular was eye watering/ego killing.

Airplane type: B747-400

Flying at 35.000 with an heavy airplane you climb to 37.000 which is just*
Possible with the weight. Reason for the climb, you are flying just below the clouds in an area of embedded TS and it is bumpy.

Starting the climb(with just a small margin between upper and lower red band but still within normal operating parameters) you notice the the wind shifting to more HW. You anticipate and notice a speed increase and start to reduce power. To no avail, the airspeed keeps inching towards the upper red band. You reduce power more( not excessively) but still, just after level of you get into the upper red band and get an overspeed warning! You reduce power even more, the airspeed drops but still in the upper red band and all of the sudden you get the stick shaker together with the overspend warning!!!

Respect the stick shaker, you add power but there is not much power left and you are on the wrong side of the power curve, increase in power does not increase airspeed so there is no other action than to descend.

As you descend trying to recover from the stick shaker you notice the wind changing again to a TW and increasing(it shifted to a HW during climb, now it shifts back to a TW) correspondingly, you notice the speed to drop even more, causing you to lower the nose even more to get out of the stick shaker.

The TW increases and the speed drops even more! During the entire event you also have the stall buffet. Somewhere, the overspeed warning stops..the stick shacker stops, you still have the stall buffet and your airspeed reads below 30(which is the minimum reading) with a large TW( in excess of 200IAS).

This all happens completely unexpected!!!! And in the timespan of about 30 seconds ( really, to the best of my recollection) you have gone from 37.000 to 22.000.

I'll stop here to see what you can make of this! I have no military training, consider myself an above average pilot), this completely caught me of guard and left me humbled enough to post it here.

Really interested to see what you can make of it and try to figure it out in a short timespan( remember, it happened to me in a short timespan)

I'll post the rest later but interested in opinions

First thought: what did the temperature do?
Second: In this excessive wind changes you will (in the real atmosphere) have turbulence like hell.
Anyway: If you have to sacrifice altitude for speed, so be it. Bad over Tibet though.

Good that your company has learned from the AF accident. I was in the sim 2 months ago, and still doing stalls at 5000ft by chopping the power and watching the speed bleed off.

You've presented an interesting scenario. No doubt the ASI indication of 30kt was due to icing, and the resulting error in the wind readout when the TAS is compared to GS.

A 15000ft loss in altitude is certainly eye opening. I still wonder why some airlines (including my own) still want us to maintain altitude during a stall recovery:ugh:

We had a session with a good unreliable speed scenario, the airplane ended up pitching up a lot, speed decaying. PF was unable to arrest the pitch up. This was a 320. When I prompted him to pitch down he said "I can't, I,m trying"
We had lost quite a few thousand feet already, the airplane slowing down and descending, the stall warning all the time. I remembered the Air France and started to use the THS handwheel to pitch the airplane down. Eventually it worked. The TRE told us later that due to some computer, I don't recall which one, the THS had frozen!

We learnt a lot.

By the way I became to two conclusions:
1- the most difficult part is realising that speed is unreliable
2- when speed is unreliable you don't know for how long it has been unreliable, you can be well in overspeed or about to stall, ergo safety is compromised and you should do the memory items, which at high altitude are illogical, but at least you have to disconnect everyithing, level off and fly a reasonable pitch with thrust as required, then troubleshoot

Certainly gives a new perspective to large thrust variations at altitude.

On the A319/320 VMO/MMO is 350/.82 , however the VD/MD is 381/.89 and structural inspection is only required from VMO + 20, MMO + 0.04. (FCB15)

So I think in general there is still quite a bit of margin on the topside of the speedband, where this does not exist at the bottom. So maybe leave the thrust and accept an overspeed?

Difficult scenario though!

The aircraft should still take 2.5g up until VD/MD btw.

Check airman,

Dude, thumbs up to you!!!

That was precisely what happened, during the climb, the pitot tubes iced over! Giving an erroneous speed increase (Alt increases, speed increases!!). For some reason accompanied by an increase in HW due to that same fault in the FMS, leading us to believe that the airspeed increase was accurate.

We reduced power for an erroneous airspeed increase leading us into an actual stall. As we recovered the alt went down and so the airspeed indication as well but this was not unnatural as the TW increased as well (due to the faulty IRS computation). Even though the low speed stall was recovered we still had the buffet ( which seamlessly went from low speed buffet to high speed buffet) together with an extremely low airspeed indication.

Short story short, when we finally interpreted the FPV and the airplane symbol, we realized there was no way we were in a stall and recovered using pitch and power settings with an unreliable airspeed situation

In the mean time, I'm ashamed to admit we had gone Mach 1.1, went from 35.000 to 15.000 in under a minute!

The entire sim session was about unusual attitude recovery, nose high speed low, nose low speed high etc, this scenario came at the end. Flying close to TS we fully expected another turbulence upset. This scenario came completely unexpected( guess some thought went into it!)

Maybe put AF in a different light.

Maybe people on here would have known better, so be it, but for me it was a humbling experience!!!!

One would have thought that after the Turkish incident in Amsterdam and AF447, AoA indications would be mandatory in transport jets. The data is already there, it's simply a matter of putting it on the PFD.

Amen to that, :ok: a real shame no-one wants to pay for it, & nobody has the cojones to mandate it :=

You raise an interesting point. No airline wants to pay for it, and no regulatory authority wants to mandate it. Yet, I've never met a pilot who would not like to see AoA in the cockpit. When it comes to safety, why are pilots not able to demand the installation of certain equipment?

I can envision a surgeon refusing to operate unless certain safety nets are in place. Why do we allow our bean counters to say that something is too expensive? They're not the ones trained to fly, we are. Shouldn't WE be the ones demanding the installation of AoA indicators?

Apropos of nothing, here's a link to a post I made regarding a sim session to perform experiments in a UAS situation.

Full disclosure : I'm not a pilot.

http://www.pprune.org/tech-log/46062...ml#post6793521

Better of bouncing along at FL350 until you have burned off more fuel and have a lot more margin for a climb :ok:

AF Pilots threatened a walkout, unless AF comitted to an immediate change out of at least one Pitot (Thales).

"You raise an interesting point. No airline wants to pay for it, and no regulatory authority wants to mandate it. Yet, I've never met a pilot who would not like to see AoA in the cockpit. When it comes to safety, why are pilots not able to demand the installation of certain equipment?".....Check Airman

Airline/Regulator/Pilots. Without all three, flying comes to a halt, sooner or later.

A Stool cannot stand on two legs.

AoA is an essential tool for accident investigators and frequently thier reports refer to it - and more than one has commented that an AoA guage would be useful for the pilots. If you have the option of displaying the FPV (Flight Path Vector) on the PFD, then you can get a good idea - the difference between your attitude and the FPV is your angle of attack. I have flown military aircraft with AoA guages and it's one of the most useful intruments in the aircraft. I once encountered an ASI failure (common on this type due to pressure changes during manouevring) - the subsequent approach using AoA and power wasn't an issue.

But one thing I noticed in the recent increase in stall training post AF447 is the lack of awareness of pilots regarding the basics. When we did our instrument training and practiced partial panel, we should all have been briefed on the basics - i.e. that flight is an equasion where Attitude = Power + Performace. Take any one element away and we can still deduce it from the other two. For example, If I take the speed indication away, I can still aprroximate the speed to fly by setting attitude against power. At most cruise levels I know that for most weights on the A320, 2.5 degrees nose up and 85% N1 will give me a safe speed. Of course, this has been reinforced in the recent training, but I was suprised at how many of my colleagues had a problem remembering it.

That is true.

I have seen many pilots have problems understanding how to fly the pitch/thrust tables in the 320. In some cases they want impossible things, like flying a given path (level, for instance) and pitch and thrust setting. You can't decide all of the terms of the equation!

I think it is due to the widespread reluctance to use thrust manually, so that when they see the table and they see a thrust setting on it, they want just to set that thrust and just forget thrust levers.

So they whole procedure becomes meaningless. The procedure states how it should be done, but I have never seen that issue properly discussed, and even some negative training regarding this procedure.

I was lucky because I was taught to fly according to that principle: . So I have no problem with that. However I have the problem of coming to the conclusion that speed indications may be bull**** and then decide or not (because it is nonsense, of course it is)

flyburg - to answer your post#1, I think it a little unrealistic! Albeit a good training 'wake up'. Firstly, the decision to climb to a performance marginal level in area of TS is wrong, even if it is (presumably?) above cloud. The wind shifts were also quite exaggerated (for the exercise, naturally).

The great result is that power/attitude (?trim- if only!!!) was re-inforced. A very difficult scenario to handle and survive!

Yep. Our parallel sim experience was similar, and just as humbling. The old "unusual attitude" training was based on you (basically) flying into it, so firstly avoiding flying into it, and secondly flying out (basically) conventionally - "stall recovery". AF447 highlighted the fact that circumstances were possible where the aeroplane could very quickly be put in a situation where the aeroplane couldn't fly, where it had also lost a lot of its instruments and protections. Still recoverable - but not like anything I've seen in 25 years of flying.

Hat tip to the regulators and airlines for getting appropriate training in place. And scaring the life out of many pilots!

The symptoms you describe indicate a frozen pitot with front end and drains blocked and the total pressure trapped inside. Did all indicators have the same symptoms?

... but this doesn't fit:

Stall recovery practice at high altitude is an important part of jet transport training for type rating. In the 737 Classic, use 37,000 ft and maintain height as speed bleeds off after closing the thrust levers. Eventually severe buffet occurs quickly followed by stick shaker. The nose is then smoothly lowered to zero body attitude at the same time climb power applied. The aircraft needs to be trimmed to hold zero body angle in the descent recovery. When the IAS reaches Vref 40 plus 100 knots (typically 230 knots IAS) it is safe to ease out of the descent and the height loss is around 3000 ft. There is no way you should attempt recovery to level flight before reaching Vref 40 plus 100 knots since G buffet will occur again and further height loss will occur.

The Vref40 plus 100 knots comes from the FCTM advice on high altitude holding without an FMC.

Low level stalling with landing flap should be conducted at the outer marker height of typically 1200 ft agl. The worst case scenario of the Turkish Airlines 737 Amsterdam accident is replicated, where closed throttles and almost full back stabiliser trim is caused by the autopilot attempting to hold the ILS glide slope.

Recovery at that low altitude is generally successful providing autopilot and autothrottle are disengaged and full thrust applied. Apply immediate forward stabiliser trim and elevator while selecting between five and seven body angle up to counteract the strong pitch up that occurs at go-around thrust. Respect the stick shaker. Leave gear and flaps at landing flap setting until reaching Vref speed and climbing. Instinctive reaction to retract the flaps to 15 as in a normal go-around procedure, must be avoided since the speed will be around Vref 40 minus 24-30 knots when the stick shaker actuates and a full stall is then unavoidable - deadly at that low altitude. There is no buffet and stick shaker is the first aural indication of a stall.

All the above is an excellent confidence building exercise and a vital handling skill in IMC.

Pan Am 707 had an event over the Atlantic with a similar scenario. Rapid switch to tailwind that exceeded the airplane's ability to accelerate. Resulted in stall/descent to regain control.

"Recovery at that low altitude is generally successful providing autopilot and autothrottle are disengaged and full thrust applied. Apply immediate forward stabiliser trim and elevator while selecting between five and seven body angle up to counteract the strong pitch up that occurs at go-around thrust."

This is too similar to what was written originally in the FCTM. No feather in my arse, but when teaching TQ I always emphasised that a stall was an aerodynamic issue and had to be solved aerodynamically. Thus, first reduce AoA and then accelerate and avoid pitching up into a 2nd stall. FCTM has since been re-written to reflect this correct technique. It may only be a split second of a twinkling of an eye, but AoA first, then N1% umph and hang on.

Gravity waves can scare you if you are near maximum FL (high weight) and the margin between VMO and VAPROT is small. In the updraft side, it makes you reduce target mach in order to reduce thrust and avoid overspeed. In this situations I hate soft altitude in the ALT CRZ mode. It makes the airplane gain some feet and increase the speed when you want quick A/THR reaction.

Then, just after you manage to recover the speed, with quite a low thrust, the downdraft side comes and everything changes to worse, the soft mode will again be late to react, some feet are lost, speed bleeds off, but in this circumstances, high altitude and low margin, gaining knots is much more difficult than losing them, so you can see the speed trend going well below green dot and the airplane seems unable to avoid the speed from decaying. And that damned soft altitude... Oh, wait, but we already have max CLB, and still unable to recover speed... Well, if then the pilot panics and decides to descend to a lower level (which is the best course of action), for Christ sake, don't let him pull for an OP DES!!!!!

I thought 'gravity waves' were things that Star Trek got?:confused:

hahaha

I meant Mountain Waves!

Anyway I think there is such things as gravity waves, which are basically mountain waves but with no mountains involved. But not sure.

Maybe I'll raise a thread about that, by the way...

Yep, I prefer to call it the "thrust idle" knob.

Microburst,
It is: power+ attitude= performance

@ BOAC,

The decision to climb was not unrealistic in this particular scenario, still some margin left. The winds changing was more due to the failure of the pitot static system an not the actual winds changing I've been told that the indications we saw were natural for the particular failure although in the real world it should have been a clue!!

@ at hazelnuts39

In hindsight, you are right, come to think of it, the speed didn't drop hence we kept slowly reducing the power.

Many mistakes made for sure, and when you contemplate it behind a pc screen the answers will be much different! However this took seconds to develop in the sim as it could be in the real world!!( think between level off and the stick shaker was about 5 seconds).

Great training, I learned something, reinforces the feeling that current training for civilian pilots is lacking. For the last 11 years I have done al sim sessions with average to above average grades and never got into any trouble. However, this was an ego killer and I learned a lot more than from the standard V1 cut, come around do an NPA on AP, GA and finish of with a hand flown SE ILS!!


Greetings

Microburst, there are indeed waves not associated with mountains. We sometime get them in East Anglia, UK, not noted for its sticking up bits. In my experience, and from what I have read, they do not generate such strong up and down velocity vectors as mountain waves, but for all I know there may be exceptions to that. Wave has also been seen on satellite photographs over the sea, far from any mountains – though with favourable conditions, mountains can generate waves a long way downwind as well as close to the triggering source.

One mechanism for wave without mountains AIUI is wind shear. Think lower high density fluid, with higher low density fluid having relative motion to it – such as sea/air interface. It seems that can happen higher in the atmosphere too, with adjacent layers.

(Glider pilot, not met man, and not ATPL)

Good form,

My first sim check, 737-8, a 30 kt crosswind, temp -20C, snowing, with an iced runway...at night, in Deadhorse, AK....

BTW...full motion ...

Buzz Nelson was running the sim...

Hopefully we can stop the flow of low time cruise type pilots getting into the airlines, then monitoring autopilots and becoming captains with no actual flying experience hand flown. It probably isn't going to be allowed to happen because of the cost by the bean counters. It wasn't like that 30 years ago, you then had to know how to fly.

Only if the air is not moving vertically. Introduce a wave or up/downdraught in a critical performance situation and that goes out the window.

Also remember the same power+attitude gives vastly different performance depending on whether you are pre or post stall. AF447 was 16deg NU with full thrust- and descending very rapidly!!

Excuse me? No competent pilot in an airliner would expect performance at FL350 heavy at a 16 degree deck angle. No ONE. We can't let these inexperienced guys be together when the experienced guy has to take his break. Get one of the old 65+ year old guys that can handle it be the second pilot as CRUISE PILOT. They would know what to do. Trust me.

Damn, I have to check more carefully what I quote!

Anyway I know you know what I meant, right?

Chrisn

Thanks a lot for that. I always wandered what the hell could make mountain waves without mountains. As for the latter, I find them very often in the same area and season, sometimes very intense.

A bit more on mountain wave. In some circumstances, a localised area can have wave that has a vertical component the same as the wind speed. Unlikely though this might seem (need a diagram here – can’t find one to post), successively higher layers can pile up on each other, with a shorter local wavelength and more bending of the streamlines from horizontal to a steeper angle, until at a certain point they go vertical. In the lee of a Scottish Mountain, Morven (Aberdeenshire) on a day with about 10 knot wind, we found local lift of almost 10 knots for a while. Mountain waves are not always the classic sine wave shape.

This might be one explanation why even airliners experience up or down drafts which seem disproportionate to the general wind speed. As far as I know, however, this extreme is only found where the mountain shapes are right for it and at the same time the airmass characteristics (wind change with height, stable layer over unstable, etc.) lend themselves to this phenomenon.

I don’t know enough met to say if it could happen elsewhere than particular spots. I certainly don’t know what happens near jet streams.

It may be that the professionals don’t yet know that much, either. A lot of early work on wave came from gliding exploration of it, before the soundings and analysis/theories followed. For obvious reasons, there is not much gliding exploration of wave over the sea.

Chris N

Oh, completely true- but that was the attitude held THROUGHOUT- my point was simply that one attitude gives two different performances- pre stall and post stall.

- not in your book, I take it, but not something I would have done with expected turbulence - whatever happened to commonsense?:ugh:CBs = turbulence= need extra margins, not less.
ChrisN and Micro - I suggest you do some met study (even Google) - and you will find that East Anglian 'waves' are indeed mountain waves, probably emanating form the Welsh uplands.

The erroneous and exaggerated wind read out is to be expected with airspeed unreliable on the Boeing that I fly (I imagine the B744 is similar). A corrupt pitot static input causes the related ADIRU to produce all sorts of nonsense. IAS, TAS, Mach, W/V, stickshaker, overspeed, GPWS windsheer warnings, even the Altimeter can all be rendered unreliable. It is a very confusing situation to be confronted with and sobbers the mind completely. It comes as little wonder when you consider how accidents occur with this sort of failure(s).

Cudos to the OPs airline for understanding and exposing this type of occurrence. All crews should be confronted with this type of training. To combine it with upset recovery is also a fantastic idea as delayed recognition or as the OP suggests, operation withinin the limits of the aircraft flight envelope, may require the correct recovery technique to be applied.

It amazes me how many pilots appear bewildered when you mention the old adage, pitch x thrust = performance. It's disconcerting when you learn that so many are unaware of the importance of having a working knowledge of he fugures found within thr Performance Inflight section for flight with unreliable airspeed or the number one thing to do in a stall is to reduce the angle of attack. Seriously.

Credit to flyburg for posting his experiences in the sim, especially when he considers how he had felt humbled by the occurrence. However I'd be pretty sure that he now feels more confident about how to recognise and confront such a scenario, a scenario which in all likelihood has greater chances of occurring than an engine failure at V1.

Sounds absolutely possible. Wind speed is calculated based on TAS and GS (and hground track). TAS itself being calculated from IAS. And herein lies the problem. When IAS is unreliable, so is TAS and thus calculated wind speed.
Also the values might be possible. When cruising at 230kts IAS while having an IAS reading of 30kts due to icing the difference would be 200kts (IAS/CAS), so the FMS would consider this difference as wind speed. However during your M1.1 adventure the wind speed reading should have been even quite a bit higher, especially, when being at a lower altitude if the IAS reading was still below 30kts.
Do you know how they did simulate the windspeed in the Sim? Is there a program to emulate all effects of pitot icing ? Or was it manually controlled by your examiner.

Interesting and enlighteneing story, btw.

regards, Henra

Nope, sorry, can't tell you how they simulated it. Will see if I can't find out.

Greetings.

Normally simple button pushes on most sims. Again, modern sims can have 'lesson plans' built in which will do the job when asked.

Low time cruise pilots
 

bubbers44 Quote " Hopefully we can stop the flow of low time cruise type pilots getting into the airlines, then monitoring autopilots and becoming captains with no actual flying experience hand flown. It probably isn't going to be allowed to happen because of the cost by the bean counters."

You are correct, of course. But although the bean counters love it, it is the regulator that allows this practice.

A well known airline based at the Fragrant Harbour uses low time Second Officers during criuse. These Second Officers do not even hold a full type rating, yet the aircraft is certificated to be operated by two pilots. This is criminal, in my opinion.

I wonder, then, what the definition of a pilot is.

I believe that the fare paying passenger has a right to expect two fully licenced and type rated pilots to be at the controls of the aircraft in which they are travelling.

Sadly, there are weak regulators who are nothing but whipping boys, merely endorsing the operator's demands.

The recently introduced MPL serves to illustrate the problem - it is not going to get any better, unfortunately.