Flying with Instrument Failures.

[Whirlybird]

The discussion of an ASI failure on another thread started me thinking about this...

Aircraft don't NEED instruments to fly. The early aviators didn't have any, as an instructor of mine pointed out to me during my PPL(A) training, when he covered the whole instrument panel and made me fly two circuits...to prove to me that I could.

However, most PILOTS need instruments to fly. I suspect that many of us wouldn't really be comfortable without at least some of our instruments. So which ones do we feel we need, and why? Personally...

Radio failure - no big deal. I carry a handheld anyway, but I'd be happy to fly and land non-radio.
DI - I'm comfortable flying with the compass; done it a lot in helicopters.
VSI - Not essential. I have a horizon, and an altimeter.
AI - not essential - often flown without one.
Altimeter - more difficult, and I wouldn't want to be in controlled airspace. But I can pretty much judge my height by the size of things on the ground, so not a problem.
ASI - As said on another thread, could use visual and audio cues, and usual power settings. However, I think I'd have a hard time with the approach, and would prefer to come in fast to a long runway. Any hints on doing this?
Compass (and no DI) - use a map, and the sun if you can see it. But I think I'd want to land ASAP if the sun wasn't around, as it's quite easy to get disorientated if you don't know which direction is which.

No instruments at all! :eek: :eek: :eek: I'd fly at the usual power settings, listening carefully to the engine. I'd judge my height from the size of things on the ground. I'd use the sun and a map to work out where I was. And I'd land on the first runway I found!

But all advice would be appreciated. I know I probably haven't covered all instruments, but this wasn't meant to be comprehensive, more a subject for discussion. I think we could help each other here. Also, may I suggest we offer advice, not say things like: "If you can't fly without a xxxx maybe you shouldn't be flying". We haven't all had the benefit of excellent training and/or loads of experience. Some of us have to become good pilots more by a DIY process than anything else, paying money we can ill afford for less hours than we really need.

Oh, and before anyone flames me for not being confident about all this stuff, may I remind you that I'm a ROTARY FI(R), not f/w...which I fly for fun, not all that well, and not often enough. :(

[englishal]

I used to rely too much on the instruments, and got a boll*cking from an examiner and failed my SE CPL first time becasue of it. So I went out with a FI who covered all instruments except oil pressure and oil temp, and we used to go out and do all of the usual manouvres, steep turns, stalls, lazy-8's chandelles totally instrumentless. We even progressed to flying back into the circuit using just rudder and trim (no instruments still) and put the aircraft in a position to land..........Didn't land it without elevator due to insurance and the risk of breaking someone elses plane, but reckon I'd have done it ok.

I learned a lot, and although a bit disconcerting to start with, you get the feel pretty quick.

The problem is recognising instrument failures. Its all very well to say "you should do this" or "you should do that" but if say the ASI is giving false readings and you don't realise it, you're in big trouble. As happened to a 727 (I think) in the USA some years ago. ASI failed in the climb, so they kept pitching up to *reduce* airspeed and eventually when the stick shaker started, they realised what had happened. They stalled, and crashed, killing everyone.

Its easy for us to say "They should have clicked that something was wrong as the airspeed was rising even though they were pitching more and more up". Still they didn't realise, and paid for it................

[tmmorris]

Hmmm...

I binned a flight last week because of failure of both AI and DI; but then it was a navex with a SRA at the other end, and it seemed a bit unfair to spring a no-gyro SRA on the poor Gloucester controller who has only primary radar to begin with.

Like you I was made to fly a couple of circuits with no instruments (did you learn at Welshpool as well?!) to show it could be done.

I think I could divide into 2 cases:

Failure of any of these in flight would cause me to divert immediately to the nearest airfield and probably declare a PAN:

altimeter
ASI
compass

Failure of any of the following before flight would cause me to cancel the (VFR) flight:

any of the above plus
VSI
turn & slip
balance ball(?)
VHF radio (yes, I know lots of you don't use radio, but you don't fly from Kidlington...)

In other words, if I lost, say, the turn & slip in flight, I'd carry on to my destination or go back home, but I wouldn't divert to the nearest airfield.

And, if the weather was marginal, I wouldn't take off without:

ADF

as that's the only way back into Kidlington in IMC (otherwise it's a SRA/PAR into a nearby military airfield and talk my way out of it!)

Tim

[maggioneato]

Regarding audio, I recently flew with a passenger who had a Bose headset, which he told me cancelled out most, if not all of the engine noise. I personally like to be able to hear my engine. I fly VFR only these days, and have flown the aircraft over for maintenance minus various instruments, I supose you would feel a misfire, but would'nt you hear it first?

[Jetscream 32]

Whirlybird,

Forget the sun, this is the UK your talking about

Flying around without an ASI really is no great shakes, as long as you have a horizon of sorts, and a few hours on type, say 10+

Concentrate on the picture outside and attitude, ensure your reference point point for landing remains constant with the aircraft configured for landing, and stay with the same power settings you have always used for all phases of the approach.

My only extra advice would be to fly a higher / wider circuit than normal to allow plenty of time for anything you feel unhappy about to be sorted out, feel etc, oh! and dont be frightened to go around with no ASI either, especially if the hedge is rapidly approaching on the approach, becuase it is highly likely you were way to fast on the first approach, if this happens keep the climbout to max of 10degrees above horizon, with full chat so that there is nearly no chance of stalling, settle down, set it up, and collect your medals from the bar afterwards!

Feel free to shoot me down,

js

[Classic]

One idea for dealing with an ASI failure is to know the RPM of the engine at gliding speed with the engine at idle. I think on the Bulldog it's 1300RPM.

If the ASI fails, fly at high power setting (ie fast) to the overhead, and then fly a PFL pattern at idle using the RPM to confirm speed.

I've tried it on a couple of aircraft and it's surprisingly sensitive on both VP and CP props. Worth considering anyway.

[Lowtimer]

Interesting thread. Having no ASI is not a huge problem providing you're not trying an ultra short field landing, just fly attitude and normal power. Of course, if any one instrument fails then you become correspondingly more reliant on he others and you lose redundancy.

I did think about this recently when the MP gauge failed on the Yak, it was before take-off so I didn't fly. Had it been in the air I would have had no real problem but it then makes you think about what if the ASI subsequently fails, e.g. wasp down the pitot on the takeoff roll.

In an aeroplane with relatively low pitch stability and a CS prop, if you had no reliable indication of either airspeed or power setting it would be a bit harder again to judge the speed, but (though I haven't tried this in the Yak) still do-able using nose attitude and the VSI. Something like the Cub with strong pitch stability and a fixed pitch prop, no problem flying in nice weather with nothing but an oil pressure gauge and a wet compass ;)

Well it's a good thing to try out dual on my next revalidation flight!

Whirly, I know nothing about helicopters. Would it be possble to fly one of those without certain instruments, or does the lack of inherent stability make it a no-win situation?

[PPPPP]

Spurred on by the other thread on this subject I today went out and did some experiments. I now know what RPMs give me a 500 ft/min sink at 70 knots for all four flap settings. It only took a few minutes and removed my last remaining fear of instrument failure.
Ok, it's a bit faster than I would like to approach but 70kts gives a reasonable margin for error and would certainly get me down safely.

[Flybywyre]

Same thing happened to me once, complete failure (due to an insect in the system) on take off from Dinard to Bournemouth. It was an early morning flight, quite hazy and hot. Just got airborne, checked the ASI on the climb out and was surprised to see it reading 100mph. Pulled the nose back to get the correct climb speed and felt a slight shudder go through the aircraft, as I was thinking to myself "that felt like a pre-cursor to a stall" the stall warning light flickered on and off. I put the nose down slightly and checked the ASI and to my great surprise it was indicating 130mph and rising !
Realising something was far from right I put the nose down and flew over Dinard at 500 feet while I tried to get my head around what was happening
Anyway, analysing things afterwards three thing where very clear.

1) The loss of the ASI itself is not the end of the world. The real threat to safety is the time it takes you realise what is going on and then to take the correct action. I suspect this can be the case with other in flight problems

2) I consider myself lucky

3) If this had have happened (during the climb after take off) in IMC I would not be writing this now

Regards
FBW

[Whirlybird]

Lowtimer,

Helicopters tend to be flown with your head outside the cockpit most of the time; with such an unstable platform as the R22 chasing the instruments doesn't work, and you certainly need to look outside ALL the time when hovering or going into a confined area. Many of the R22s I've flown have only basic instruments - compass (but no DI), altimeter, ASI, VSI. I wouldn't worry if the ASI failed, because airspeed is not so crucial in a helicopter. I wouldn't care too much about the altimeter or VSI either, so long as I was outside controlled airspace. If the compass failed and I didn't know where I was, I'd land in a field near a road and then sort it out...or fly low and slow(ish) and follow the roadsigns. You see, we do have those as options. :ok:

However, one thing is absolutely crucial for helicopters, and that's rotor RPM. On most modern helicopters the engine (and therefore rotor) rpm is controlled for you by an electronic governor. If the governor fails, you have to adjust the throttle youself, by reference to the tachos, keeping the rotor rpm "in the green". Helicopters have a mechanical correlator to help you,; it's not usually that good, but so long as you've practised, governor failure should not be a problem. I've flown a few ungoverned helicopters now anyway, so I'm more used to manual rotor rpm control than I used to be. If the rpm tachos failed you have a low rotor rpm warning light and/or horn on most helicopters; you could adjust your rpm using audio cues, and know if it's too low by the warning light/horn. If you had no governor, no tachos, no light/horn...shouldn't happen (in the R22 all are on separate circuits to prevent it), but not a nice situation at all. You'd have to rely on audio cues, and how difficult it would be depends on your own experience AND the type of helicopter. The R22 has a very narrow green rotor rpm band, and would be quite hard; the Schweizer 300 series have a much wider range and you can hear it fairly easily. But in practice, to hell with that; if they really all failed I think I'd declare a Mayday, land in the nearest field, and sort out it all out on the ground.

Any other helicopter pilots care to comment?

[TheKentishFledgling]

In a helo, is losing the ASI as serious as it would be in a FW aircraft?

(by serious, I'm not saying you can't fly without one, but I'm sure most of us would rather have it than not!)

tKF

[NATCA A80]

I was flying once with someone when it was IFR and most of the instruments decided to take a vacation. The pilot very calmly pulled the piece of gum out of his mouth, and a small ball with a string from his pocket, and stuck it to the top of the dash where it could hang free. His theory was if the ball was hanging toward the ceiling we were upside down, all the way to the right, we were in a tight right turn, hitting us in the face in a steep climb,(you get the theory).

Anyways he told atc that his instruments had failed and needed to descend down to VFR below the clouds. The descent was uneventful (I think that he had done this before).

Now you understand why I'm a controller and not a pilot, I can't chew gum and fly at the same time.

Mike
NATCA A80

[Whirlybird]

tKF,

In a helo, is losing the ASI as serious as it would be in a FW aircraft?

No. On the whole, airspeed isn't crucial in a helicopter. Helicopters don't stall at low airspeeds. At very low airspeeds, with a rate of descent and power applied, it is possible to get into Vortex Ring, which roughly means you descend in an uncontrolled manner through your own downwash...and fall out of the sky if you don't catch it in time. However you need less than 30kts airspeed for this to happen, and it would be unlikely even with a dodgy ASI. If I lost the ASI in a helicopter I think I'd just use outside references and my other instruments, and carry on as normal. If I couldn't fly in VMC I'd land, but I'd do that anyway.