Instrument failure

[abc1]

I have a question on Instrument failure/unreliable instruments due blocked static ports, case of Aeroperu flight 603.
Using this scenario how would you deal with it(especially if you are a 75/76 pilot?
Was there sufficient information available for partial panel flying?

[PantLoad]

Pitch 'n Thrust

Pitch 'n Thrust....You can use GPS for altitude information at higher altitudes, and the RADAR altimeter when lower.

Never flew the 757/767, but the basics are the same on all aircraft.
There should be a written procedure for such an event.

Fly safe,

PantLoad

[john_tullamarine]

Often listed in the QRH as "Flight With Unreliable Airspeed" or similar.

One should have enough attitude/thrust combinations in the mind to be able to fly reasonably well without reference to the book but it helps to refine things in the real world situation.

He who has no idea of the combinations eventually is in line for a rude awakening when it does happen ....

[Tmbstory]

Instrument Failure Pitot / Static

Do not forget the simple un- sophisticated direct reading outside air temperature gauge will give you an indication of climbing or descending and therefore help with your estimate of altitude.

Tmb

[hetfield]

Not to forget:

- weather radar, 1/60 rule
- if you can assume to be below 10k feet, depressurise cabin and use cabin alt indication (based on 1013 but better than nothing)


NOTE

I'm not current on 757/767

[Rainboe]

One of my colleagues had a case of unreliable airspeed on the 757. Ably coped with by pitch/power flying. Not to be discounted is the severe disorientating effect of high speed warnings with zero airspeed, and stick shaker with absurd high speed readings, klaxons and warning lights. It is a time to try and calmly stick to basics. Certain recent past accidents could have been prevented by focusing on the right information-INS groundspeed is near enough TAS to keep you alive. It will be rare to lose all visual references which could help- at night time staying near illuminated areas might assist in retaining orientation

[A37575]

Do not forget the simple un- sophisticated direct reading outside air temperature gauge will give you an indication of climbing or descending and therefore help with your estimate of altitude.

Tmb

Brilliant, Tmb. I would never have thought of that one. Must try that in the simulator.

[A37575]

It is a time to try and calmly stick to basics.

Agree wholeheartedly. But try convincing regulators and airline check pilots that pure instrument flying skills should be accented in simulator exercises rather than the current blind continuation of automatics.

[Fratemate]

I hope I'm not going to confuse similar incidents but I seem to recall from the AeroPeru accident that they managed to get up and away but it was getting down again that was the trouble. It's easy enough if you've got an ILS to slide down; in this case it's just a matter of getting on the glideslope, setting the recommended power settings from the book and erring on the slightly fast side if confused. As already stated, there's other information around ATC, IRS groundspeed etc, so it's not all lost. If you exceed a flap speed and damage a couple of panels, hey ho, at least you're alive. However, if there's not an ILS you can use (or PAR) then it becomes a whole new can of worms. Is it possible to descend over the sea and use the radalt until you can see what's underneath the cloud? Is it possible to have a shepherd aircraft (military) join you in formation and (a)lead you in the right direction and/or (b)give you the information you need; speed, altitude etc, these things would go through my mind but I am lucky enough to fly in an environment that has ILSs all over the place.

I believe this incident was the catalyst for getting attitude/power settings put in the QRH. I'm not going to argue if somebody tells me that ain't so but I don't recall them being on the 757 until after this accident (it may well have just been my company at the time).

As Rainboe says, the din of clackers, shakers etc going off cannot be ignored. It only takes a climb of a few thousand feet with the pitot tube blocked and the poxy overspeed warning goes ballistic and this is distracting enough to seriously affect judgement. As good a reason as any for most companies collaring the appropriate CBs, so you can pull them and get rid of the spurious noises as soon as possible.

What about opening the DV window and using the escape rope as a 'sounder' ike the ships of old? "How many fathoms till touchdown number one"

[Tmbstory]

Instrument Failure Pitot / Static

A37575:

Thanks for the comment, in the 1960's we used to do a lot of cloud seeding in a Cessna 310. When seeding strataform cloud it was a requirement to seed at the minus 5 degree C level. That is where I first found out about the value of the outside air temperature gauge.

Regards

Tmb

[abc1]

Thanks for your replies so far.
I am familiar with Pitch/attitude settings and constantly refresh my self with the numbers, however having never experienced either a blocked pitot tube or static ports I was after some more expanded views.The QRH merely has just enough rope.
In the case of the Aeroperu, they seemed to be overwhelmed by the array of bells and whistles. The same happened to the Birgenair flight that suffered a similar instrument failure. Then simulator studies were carried out and concluded that the amount of conflicting information took the better of all crews tested.
I admit its easier said than done to comment from the comfort of the armchair but it seems that basic flying skills, partial panel flying was not exercised due to the overwhelming information being thrown at them.
Lets look at what was available in terms of instruments:
Is the VSI on the 75/76 not fed by the IRS's?
Attitude, Heading,Radio Altimeter, stby compass, radar vectoring, what else was available?
How would you prioritise?

[UNCTUOUS]

I breaka your face...

Blocked static source (e.g. frozen water in the lines) - ASI will quickly slide back to zero in the climb and VSI will zero, altimeter will stick. Just depressurize and break the glass in the face of one VSI - as an alternate static source. Altimeter and ASI will be good. Other VSI should be no good.

[BOAC]

abc1 - do NOT forget that each pilot should be aware of the other's instrument readings - ie the odd 'cross-check' would have avoided one of the incidents mentioned here. If you have 2 of the 3 ASI's or altimeters in agreement..................It is not a bad idea to try and cover up the misleading instrument either to minimise distraction.

INS or GPS groundspeed is of no use at anything other than low level except as an indication of whether you are accelerating or decelerating. Aeroplanes fly and crash because of IAS, not GS or TAS.

If, heaven forbid, the worst happens to you -ALL sources are out - and you are sitting fat and happy with the correct pitch and power, ignoring all the false warnings and just wondering how you are going to get down, hetfield's suggestions will help a lot. Getting out over some oggin would be nice too, where the Radalt will safely give you a cross-check. After that, you need to find an ILS or PAR, hopefully in reasonable weather, which is reachable at a 'safe' altitude that you can confirm.

Don't forget - we're all counting on you...

[FullWings]

Another useful item in a glass cockpit when pressure-driven instruments are offline is the Flight Path Vector - if one's fitted, of course!

If you want to fly S&L, which is a good idea while you sort out what's working and what isn't, just manoeuvre the 'bird' onto the horizon: that stops you going up or down. You can then set a datum power from your 'flight with unreliable airspeed' tables.

If you keep the gap between the pitch bar and the FPV constant (c. 2-3degs in the 777, probably not too different in other jets), then you'll be somewhere in the middle of the speed range for your configuration == safe. If you notice the gap reducing, you're getting faster and vice-versa. It's a good cross-check against other sources of information - effectively you're flying AoA and should be able to approach and land without reference to any other instrument...

[Graybeard]

AeroPeru had blocked static ports (and pitot?) - at 3am local. The 757 has Digital Air Data Computers, so breaking glass could not help - there was no static plumbed into the cockpit.

I'm sure they did not know blocked ports were at fault; they were just overwhelmed with nonsensical info and alarms. Recovery would have been luck as much as skill.

GB

[Ka8 Flyer]

FullWings,

are you sure the flight path vector does not require air data?
While the IRU's do have vertical acceleration as an output (that's where the Instantaneous in IVSI comes from and the reason the VSI needle will jump around 0 when climbing / descending with statics blocked), I do not think that vertical velocity is also an output. So where would the vertical trajectory info come from? NSEU - any clues?

[FullWings]

are you sure the flight path vector does not require air data?

I can't speak for the manufacturers but mathematically, no it doesn't. The reference platform senses accelerations and integrates them over time to give attitude and position (and from that the flightpath)... Air data not needed.

One way of losing pneumatic input is a birdstrike - often there are several birds involved and they can easily mangle your AoA probes on the way past, so IRU derived data is most likely to be correct at that moment.

[john_tullamarine]

I admit its easier said than done to comment from the comfort of the armchair but it seems that basic flying skills, partial panel flying was not exercised due to the overwhelming information being thrown at them.

I'm a few years out of touch with the training world these days so my views may be quite saurian.

In days gone past effort was spent in sim training, especially on endorsements (where some spare time could be teased out of the published program), to challenge the student with a variety of failed instrument situations.

Provided that the individual's self confidence was monitored (such exercises are pointless if the end result is not a confidence boost), the very great majority, including 200 hour airline cadets, were more than able to manage a "total" pressure and related instrument loss in adverse weather conditions provided the exercises were incremental and where "total" relates to just what you might be able to achieve in a given box.

For the 737 we generally managed to lose everything and those things we couldn 't fail, we covered up the gauge so that the end result was the same - with the aim being to lose all information which would provide accurate height, speed and position data.

For the more confident student we would end up with a simulated crew incapacitation (ie a single pilot trip) and Cat 1 recovery with a handflown raw data approach and landing in light wind conditions.

The effect on the individual's I/F confidence was manifestly evident and it was always a great buzz to see a guy (or gal) float out of the box with a head circumference markedly larger than that with which he (or she) entered the batcave sometime earlier ...

The other aim of such exercises was to impress on the student the imperatives -

(a) knowing body angles and thrust settings for configuration and flight stage

(b) "looking through" the FD so that the I/F cognitive process was an integration of raw data and FD guidance. Without this it has always been my view that the pilot is set up for bells and whistles distraction from the recovery task at hand.

[Loose rivets]

I used to preach using a turn and slip to check on the health of the horizon.

One very dark, but fortunately still night, I kept correcting things to the point I had to pop out and look at the horizon under the stars to find that the T&S had failed and I'd precessed all the gyros out of kilter (a technical term)


One should always remember that these things happen in real life. I'd just finished my sim training on the ATR and on my very first flight as skipper under training, the EFIS horizon sloooooooly went belly up.

[411A]

But try convincing regulators and airline check pilots that pure instrument flying skills should be accented in simulator exercises rather than the current blind continuation of automatics.

Not a problem at our outfit, the autopilot stays OFF except for CATII/III and the odd holding/NDB approach, during checks.