View Full Version : Another great sim scenario!
One of our colleagues has been given this recently:
During the takeoff roll, all four hyd pumps illuminate low press at about 100 kts! (B733)
The poor guy decided to continue, and he was absolutely right I think, as you are not supposed to look on the overhead panel when you are PF on the takeoff roll, and these failures don't make the airplane unable to fly.
In fact, he flew a perfect circuit, and came back OK.
He was then criticised for not having aborted!
Now, dear ******** TRE, if you hear me, not only your scenario is ridiculous, as suddenly and simultaneously losing all hyd pumps at 100kts can only come out of your sick imagination after a sleepless night spent trying to reinvent your own wheel, but criticising the decision to continue is pure horsedump. :mad:
LEM
Alaskan Timber
10th May 2005, 08:05
What is your OM A (GB) saying about aborting take-off after 80 knots? Show this to the TRE and ask him how long the runway was.
eagerbeaver
10th May 2005, 08:08
yeh, but aint that just the way most of the time. Better to have done it in the sim its another possibility explored.
I always take criticism as positively as possible, if it becomes annoying listen but dont take it to heart.
There is always someone who thinks he knows more.
Gary Lager
10th May 2005, 09:59
No (well, almost) sim scenario is ridulculous - have a look at some of the radar replays at LTCC or leaf through the accident report archives.
(Double engine fire AND gear won't come up? That'd never happen...except to concorde...)
Just because I flew a 'perfect' circuit (although I don't think I've EVER flown one of those) after a problem on TO, doens't mean I wouldn't be ready to listen to criticism of my decision after the event...I'd rather have the benefit of hindsight after a SIM session than need it in the real world!
Of course, my ability to process such criticism in a constructive manner would depend to a large degree on it's style of delivery. An intelligent discussion, perhaps based on something I hadn't realised: great. Someone telling me that I was 'wrong', with little useful feedback: hmmm...I may well be, but am unlikely to be convinced.
Though you didn't mention explictly the subsequent course of events in the sim, LEM, from what you say I would have thought more criticism would be directed at the resolution of the problem with a circuit to land, rather than (as most would prefer) as long a time as possible in the hold prior to landing, burning off fuel, becoming completely happy with the degraded handling of the aircraft, briefing full for an emergency landing etc etc. Total hydraulic failure needn't present any real problems flying the aircraft, but there is lot to be considered before starting an approach.
The other thing to consider, of course, is a failure of the low pressure warning system itself - though probably unlikely on both systems simultaneously. There may be time for the PNF or even (briefly) the PF to have a quick glance at the HYD Quantity & Pressure gauges to see if they present the same picture. Whilst time is indeed short on the takeoff roll, it may be far better to make the correct decision at 120kts than the wrong one at 100kts.
All just points for discussion, and unlike your TRE, I'm not prepared to say either I or your colleague are definitely right or wrong!
FullWings
10th May 2005, 16:35
During the takeoff roll, all four hyd pumps illuminate low press at about 100 kts! (B733)If my memory serves me correctly (it's a long time since I flew these) you might not have any thrust reverse/nosewheel steering, etc. and you may, depending on how/when/where the hydraulic failure(s) occured, be left with compromised braking. Hardly a good configuration to have the airframe in for an RTO on what might be (and probably will shortly become) a limiting runway!
It seems to me that the more modern an aircraft, the more warnings are inhibited in certain ways during the latter part of the takeoff roll and the first bit of flight. This has obviously been a conscious decision on the part of the manufacturers, backed up by decades of data. Certainly the industry has become more "go minded" since I began flying and there are many examples to support this philosophy quoted by the proponents of this cause.
I think it's very difficult to assess the effect of an unusual problem on a) continued flight or b) stopping performance and to make a judgement as to which is the safest option, all in a few seconds. I would go as far as to say that unless you have grave doubts about the aeroplane's ability to fly, you are giving yourself a better statistical chance of success by taking it into the air and considering your situation there.
An extremely unlikely scenario, and I agreee with LEM, but it has got people talking!:D
IF it was only 'criticism' in the debrief and not 'FAIL' then does it really matter?
You are quite correct, LEM, you should not HAVE to look at the o/head assuming you have a 'competent' P2 who, as briefed, notifies PF of the failure or, if Captain, calls 'STOP' or 'CONTINUE'.
It is ALWAYS Captain's decision. 20/20 hindsight will always apply. NB Runway length etc not given here.
PS LEM, is this the same TRE?:D
Gary Lager
11th May 2005, 09:10
Total HYD failure would still leave reversers available through the standby system (though deployment times increase), along with accumulator braking, availability of which, as usual, is governed by the number of brake applications rather than braking force reqd. I think anti-skid is still available as well. So, RTO ought to be possible but not necessarily the best idea - it depends on a lot of things, as discussed above, and as it ought to be be discussed in the de-brief.
Interesting to note that Mr Boeing has covered himself well - all the associated QRH procedures and performance data (at least in our outfit) are referenced to LOSS of System A (or B), not any particular caution light - assuming, once again, that that has been correctly diagnosed as the actual condition of the aircraft. The Low Pressure lights are just one clue to what is happening.
Alaskan Timber
11th May 2005, 10:16
Anti-skid with accumulator brakes is not working. Further are the ground and flight spoiler not working either.
rgds,
A.T.
Capt Chambo
11th May 2005, 12:05
From my copy of the Boeing QRH (Albeit it for the NG series).
Above 80 knots and prior to V1, the takeoff should be rejected for any of the following:
Fire or fire warning
Engine failure
Predictive windshear
If the aeroplane is unsafe or unable to fly
From an old copy of a flying manual for the Boeing 733. Boeing recommended that once thrust has been set and the take-off roll has been established, rejecting the takeoff solely for the illumination of the amber MASTER CAUTION light is not recommended.
It would seem to me that unless your colleague's company SOP's dictate otherwise he was absolutely right to continue the takeoff if the scenario was as you described, and the TRE has no case!
Hi BOAC, no it's not the same one...;)
Hi Alaskan Timber, antiskid is supposed to work fine on accumulator pressure.
I don't have any more details on rwy lenght etc..., but I know that guy is not nice at all. :yuk:
Hi BOAC, no it's not the same one... - you ARE a lucky lot, then..........:D
Clarence Oveur
11th May 2005, 17:37
antiskid is supposed to work fine on accumulator pressure
Or how to deplete your accumulator awfully fast.
Alaskan Timber
11th May 2005, 19:50
Lem,
Actually you are right regarding the anti-skid. On the "classic", the last amendment (dec 7 2001) the sentence, antiskid protection is available even with loss of both hydraulic systems, has been added to the Antiskid Protection chapter.
On the "NG" this has not been added. Where the chapter Antiskid Protection says that antiskid protection is provided in the normal and alternate brake systems (nothing is said about the accumulator brakes). I "guess" they forgot to amend this one. I will ask my fleetchief to check this with Boeing.
Anyway good that you challenged me to check both my FCOMs.
Hi Clarence Oveur, well, not really...
The accumulator alone is supposed to provide at least six full braking applications.
The policy while braking after such a failure, like manual reversion, is to apply steady brake pressure, without modulating.
While technically speaking it would still be possible to abort after losing all four pumps (you still have full braking capability and -slower- reversers), my points against this are:
the PF MUST look outside and not above, everybody knows aborting is much more dangerous than continuing, flying on cables only takes some more beef but is not difficult or dangerous at all, and the QRH clearly states that you don't abort for a master caution above 80kts.
Don't tell me the airplane is unsafe or unable to fly on cables only :*
"It is ALWAYS Captain's decision. 20/20 hindsight will always apply."
There MAY be occasions when I might prefer to stop. It should be a 'discussion item' as I said - and you are quite correct - using antiskid NOT a good idea.
The Real Slim Shady
25th May 2005, 09:51
This link (http://www.boeing.com/commercial/aeromagazine/aero_11/takeoff.pdf) is a Boeing article on RTOs which you may find interesting
MMEMatty
27th May 2005, 16:35
forgive me for i'm just a student, but from what ive learned if you have a failure of a major system (i.e. hydraulics) before V1, surely you are required to STOP?
As i said, ive never flown anything larger than a Piper Archer, so i dont know for sure, but that is my understanding.
Matty
FullWings
27th May 2005, 19:40
MMEMatty,
Click the link provided by The Real Slim Shady. It says most of it, really.
How typical is that type of failure ? or was it just bored sim instructors looking for new stuff to do ?
After a chat with the TRE in question, now I see more clearly what his point was.
A tyre burst could severe BOTH A and B reservoirs lines, thus leaving the airplane with all four hyd pumps low pressure illuminated.
In this case, the airplane has to be considered unsafe, as the oil from the STANDBY system returns to the - destroyed- B tank.
So, eventually, you would loose ALL pressure to the rudder.
If an engine fails, you are dead (unless you close the good engine also and glide to a good spot...;) ).
He is right in saying that the condition UNSAFE is one of the reasons to abort above 80 knots.
BUT..........
WHAT ABOUT ABORTING THE TAKEOFF WITH BURSTED TYRES????
In my opinion, that's a guaranteeded overrun.
So we have to balance two risks against each other: the remote possibility of an engine failure, and the almost certain overrun.
What would YOU do?
As people often ask what the hell does the word "unsafe" exactly mean in the list of the non normal manoeuvers that deals with reject takeoffs, our dear friend at last had the illumination:
academically, yes, he is right: with all four pumps illuminated during the takeoff roll, the airplane is unsafe.
:zzz:
Itswindyout
3rd Sep 2005, 05:18
IMHO, the STOP call would be based on different situational call in regard to the actual take off brief.
The time frame between the problem and V1, as well as the actual ground conditions, are also relevent. There are good arguments to continue a take off when the book suggests ( demands) an abort....the classic case being a tyre burst, or a two tyre burst at V1-5. (say)...on a length critical take off. The question that is not covered by the good book is....would you rather try and abourt with an unpublished STOP distance, with a MAX weight aircraft, and thus at very high weihg...or heaven forbid..ignore the book. thake the problem into the air...take several deep breaths, consider the problem rationally, and burn off the fuel, find a loooooong runway, with a fire department who has finished the current issue of Beano (sorry Luton), then land at a vastly reduced speed and weight in the first not last third of the runway...and have all the gods on your side.....
Not certain which call I would make....lol
I leave the specific question to typed and current pilots to discuss for you...
windy
alexban
3rd Sep 2005, 16:39
How do you think a burst tyre will result in a severe of both A and B reservoir lines on a 737? Would it be physically possible?
I guess not,no way for some piece from the burst tyre to enter the main wheel and severe the lines.
Even if this would be possible you'll have the stby sys for take-off.After that,even with stby disabled,an engine out would be survivable at higher speeds. For landing,I'll do as you said,come to a good position,then reduce the working engine,and glide for landing. (done in the sim,210 kts,flaps up,both eng off,did ok).
To reject at high speeds,with tyre(s) burst would be 100% overrun (did that in the sim also)
The oil from stby will return to tank B...hmm...not true
" A leak in system B does not affect the operation of the stby hyd sys" 13.20.3
Furthermore,the stby sys works with the stby rudder pcu,not the same one used by A or B sys.When in use ( flt control switch to stby rud) the related hyd sys shutoff valve will close,isolating the system.
So ,I suggest, you tell that TRE to review the hydraulics chapter as there've been some changes done.:ok:
windy: for tyre burst the 'book' recommends to stop if only bellow 80 kts .Above 80 you should stop for eng fire,failure,aircraft unable or unsafe to fly,predictive windshear.
The definition for unsafe it's a bit tricky.Actually,it gives you the option to reject a take-off due to any reason that you can qualify as an unsafe situation on your oppinion.
Hi alexban, as you say the bursting of tires is very unlikely to severe the hyd lines, I think.
Maybe it's possible, but...
That was his idea for the illumination of all 4 hyd pumps low pressure.
That's not realistic, as I've said since the beginning.
And, as you say quite correctly, the loss of system A and B fluid will not cause the loss of the STBY system.
Probably his idea was that the tyre burst severes also the STBY lines...
I can imagine him saying: "If ALL pumps are illuminated that means a major structural failure! Don't you think the Standby will also be affected??!"
I still think his scenario doesn't make sense.
BTW, if any of you has got other ideas on what could cause the sudden loss of ALL four pumps during takeoff, please tell me :{
alexban
5th Sep 2005, 06:59
Inflight,with a very low OAT ,you can see all pumps illuminated,it happend this year to a few NG ,flying high and with a very low temp.They had to descent to lower FL.It was not a 'major structural failure' as you see ,but can give a ideea of one reason why you can see all hyd lights on.
One other reason I can think off will be a major blast in the wheel well area,but in this case you will feel it for certain in the cockpit:} For sure you won't have time ro remark the hyd lights.... :ugh:
The TRE may have read about the DC-10 accident,but there is no resemblance with a 737 (no tail engine to severe all lines,a different pcu for the stby....)
Contaminated hyd liquid may cause the lights to come on,but you'll check during walk-around for this condition.And I doubt would happen to both sys at once.
You can tell him that 'if all pumps lights on-major structural failure ' (big blast maybe) it won't be a problem of continuing or not of the take-off.It would be a problem of emergency evacuation.
Inflight,with a very low OAT ,you can see all pumps illuminated,it happend this year to a few NG ,flying high and with a very low temp.
Quite interesting!
You never stop learning:ok:
NigelOnDraft
5th Sep 2005, 09:41
LEM....
You seem to somewhat misleading us... deliberately?During the takeoff roll, all four hyd pumps illuminate low press at about 100 kts! (B733) but only a page later A tyre burst could severe BOTH A and B reservoirs lines, thus leaving the airplane with all four hyd pumps low pressure illuminated These are very different scenarios... An isolated inexplicable set of warning lights is not the same as a loud bang, probably swing, AND numerous warning lights.
The first tends one to think of being "go minded"... the second is more Stop territory....
alf5071h
5th Sep 2005, 09:58
The instructor who thought of this scenario should seriously reconsider the probabilities and hence the training value. A simple reference to the certification requirements or cross check with the manufacturer will help put things into perspective.
This issue is symptomatic of many of the industry’s training problems – the human fascination with the extreme – where we tend to over focus on the rare situations; humans like to fantasize ‘what if I was there’ and ‘how would I have coped’.
For example, there have only been two notable loss of flight control accidents in 10 years, but lets assume 1 rare situation of this severity per year. However, there are at least 5 major commercial CFITs and over 20 overruns per year just for starters; these and other accidents are the key issues to focus on. Many of these ‘routine’ events are actually failures to correctly identifying the situation; the training must address the threat - a possible imbalance of 25:1 with an incorrect focus. The real threat situations are dominated by human error; many instructors contribute to this with an inappropriate focus on rare events.
Attempting to fly with no hyds most probably will result in a crash, stopping without brakes, a similar result, what’s the training value? This is a confidence destroying and negative perspective of incorrect situation assessment / decision making in an unrealistic scenario.
There would be more training value by generating a loud bang before / after V1 without any warnings. To make the bang unusual and surprising try dropping the Jep bag on the sim floor! Then induce severe vibration; is it engine or tyre? But the important question / decision is stop or go!!!
Hi NigelOnDraft, if you read with more attention you'll see that the whole story happened to one of our colleagues, not to me.
So I reported what the tam-tam made available to some of us.
What happened is all four pumps illuminated before V1.
I'm not sure there was an audible bang or not.
Misleading deliberately?
:zzz:
alf5071h,
excellent post, outstanding!
These are exactly my thoughts, as especially here some instructors like to set up very complicated and tricky scenarios, with multiple failures and so on....
when we have people having a hard time flying a manual circling or go around!
Empty Cruise
5th Sep 2005, 17:17
Re. sim scenarios...
The scenario your colleague was given, LEM, could have training value - as a discussion point. I think that all the excellent replies above show that the isolated illumination of all 4 pump low press lights is not in itself a cause to abort, but further circumstances might make the stop call the only right call to make.
The problem often occurs when the TRI/E in question brings along an "eye-opener" scenario - but with a pre-concieved "correct" crew reaction & outcome. The eye-opening scenarios are great, but the crew have to sort it out for themselves. Only if they embark on an obviously dangerous course of action can you start giving out and using phrases like "Next time around, a different approach might be warrented, gents...". That - BTW - is one of the good things about instructing. You are suddenly treated to new approaches that you had not thought of yourself - approaches that might very well work, that is.
So - good scenario, but put to dubious use :ouch:
Brgds fm
Empty :)
CaptainSandL
5th Sep 2005, 20:15
Alexban,
Re:
“Inflight, with a very low OAT, you can see all pumps illuminated, it happened this year to a few NG.”
This was a known problem on NG’s due to water trapped in the reservoir pressurisation system which froze when cold soaked and blocked the reservoir bleed air supply causing cavitation at the pumps. There is a mod available (SB 737-29-1106) which fixes this and another problem. You can tell if your aircraft has been modified because there is only one reservoir pressure gauge in the wheel well.
Re a double (or triple if you count the standby system) hydraulic failure on take-off: It has not happened in 38 years of 737 operations and I can’t see it happening, but nothing is impossible in aviation.
S&L
Empty Cruise, I like your post too :ok:
A37575
6th Sep 2005, 13:42
These impossibly idiotic scenarios described above have been a feature of simulator "training" for decades. Management pilots who dream up this nonsense get bored with routine simulator sequences and we all know that the Devil makes work for idle hands. We had similar nonsense at Central Flying School where as part of an instrument rating test in a Dakota, one had to perform a single pilot, asymmetric, limited panel (no AH or DG) NDB aurul null instrument let down.
The recent dreadful accident in Indonesia where a 737-200 of Mandala Airlines appears to have done an airborne abort seconds after lift-off (gleaned from notoriously unreliable media reports), is one accident where simulation of the events could be demonstrated in a simulator to show the potential for disaster caused by a late decision to abandon a take off. It looks like the Mandala 737 may have suffered an event very late in the take off run that for some reason caused the captain to abandon the take off- - with disastrous results.
Rather than invent complicated and highly unlikely non-normal scenarios such as those described in this thread, there would be better value if crews were given an event at V1 or VR or even V2 that has previously happened in real life and which has caused a reflex abort action which proved quite dangerous
For example, a door warning light coming on, or a generator failure light, or a reverser actuation - things like that which require fast and correct action.
I-2021
3rd Nov 2005, 16:44
Lem I totally agree with you but the analysis that the TRE made is obviously right from a theoretical point of view but not so easy to apply in an actual situation I would say. At that speed you are so close to V1 that this kind of analysis is really unlikely. One thing is if you hear a big "bum" of bursted tyres and then you get the 4 hyd pumps low press. Probably you are not really understanding what's going on but you feel something will be unsafe to fly very soon and you stop. Bursted tyres + accumulator press only will maybe lead you to an overrun... on the other side if you go, you fly manual reversion (not a big deal) al low speed and maybe you will also loose the stby hyd... and if an engine fails you die... ok but come on ... both the cases (ovverrun and go decision) are extreme...
I would have done exactly what you did in the sim, especially if I had wet runway or LVTO.
AirRabbit
3rd Nov 2005, 19:18
I completely agree with BOAC in his earlier post – “but it has got people talking.”
Unfortunately, there are a lot of “unanswerable” questions in this business. Do you “go” when you really shouldn’t? Do you “stop” when you really shouldn’t? What IS the right answer? There probably isn’t a single right answer. I’ve always thought it better for me to consider what I would do under similar circumstances and, hopefully, talk about it with some of my colleagues. I’d much rather do that than have my colleagues stand around my head stone and talk about what I could have or should have done!
_______
AirRabbit