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

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.

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.

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!

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

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.

Anti-skid with accumulator brakes is not working. Further are the ground and flight spoiler not working either.

rgds,

A.T.

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:

- you ARE a lucky lot, then..........:D

Or how to deplete your accumulator awfully fast.

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.

This link is a Boeing article on RTOs which you may find interesting

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

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: