VFR to Inadvertent IMC Escape

[jungle drums]

Hi All,

Can anyone help me find an old thread that I should have bookmarked?

Sometime ago on this site there was some talk about options that a VFR Only pilot in a VFR Only aircraft could use to descend to cloudbreak should they ever inadvertently become IMC without IFR training and equipment, or should everything become overwhelming.

One of them was along the lines of 'trim to minimum speed and let go of the stick and keep the compass on heading with rudder' or some such thing.....

Is this thread here on pprune?

thanks for any help....

[Stratus Fractus]

Hi, Can't help you with the thread but this is a REALLY good read which is related to your query:

Pelican's Perch #26:<br>No Pisco Sours for Me, Thanks! (http://www.avweb.com/news/pelican/182096-1.html)#

Hope the link works. If not its the excellent "Pelican Perch" column, Article No 26 over on Avweb.

Cheers

SF

[bingofuel]

You may be thinking of the technique that you set the aircraft up in a descent heading south, keep the ball perfectly centered, then lock your feet and try to hold the heading on the wet compass with aileron. The theory is that heading south (in the northern hemisphere) has the least compass errors whilst turning.

But I only offer this as a suggestion and take no responsibility for its accuracy or effectiveness!!!!

[BackPacker]

Wiser men than me will surely be around to discuss all sorts of inadvertent IMC survival strategies. But there's one thing I've heard a few times now and that is if you ever get stuck in IMC with nothing but a whiskey compass to maintain direction, while descending or climbing to get below/on top, you'd better fly due East or West. This gives you the most direct reading of any turning tendency, since when flying North or South, the compass is either overly sensitive or lagging behind (and I always forget which is which).

[Pace]

JungleDrums

The first thing to do is to use your radio and tell them of your problem.

A blind descent through cloud when you have no idea of where you are and have little idea of the cloudbase is very risky.

A blind descent into terrain is not a clever move. The last thing you want is to be even thinking about your track over the ground let radar be your eyes so you can concentrate on keeping the wings level.

On a lighter side a method for descent through cloud while staying roughly in one spot in aircraft with little in the way of instrument flying equiptment was to spin through and break the spin when you came out of cloud :) (not sure whether I would advise that)

Pace

[BackPacker]

On a lighter side a method for descent through cloud while staying roughly in one spot in aircraft with little in the way of instrument flying equiptment was to spin through and break the spin when you came out of cloud (not sure whether I would advise that)


Heard that trick too, but would not advise it either, unless the aircraft is cleared for intentional spinning, you know the spinning characteristics intimately (beyond the standard three turns - you might need a dozen or more turns to get through a layer) and you have a guaranteed cloudbase of at least 1500'.

Not for the faint of heart...:=

[FlyingForFun]

Maintain a heading of South would make sense to me.

It is true that a compass has no turning errors on east or west - but it does have acceleration errors, which would come into effect as you were pitching/trimming for the descent.

On South, the compass over-turns (in the northern hemisphere). So, if you are maintaining a heading of South, and inadvertently enter a left turn, the compass too will turn left, but more so than the actual amount you've turned. And vice versa for a right turn.

On the other hand, though, the original question was asking about a VFR aircraft. Surely most VFR aircraft have a DI, and even an AI? In which case, just use the instrument flying skills which you learnt on your PPL!?!

FFF
------------

[hooligan88b]

I went out in one of those very poor vis days that turned in to marginal IMC then almost full IMC very quickly in a Rand KR2 once. No DI or AI and a very wobbly turn co-ord and a fairly twitchy little machine anyway. Anyway it was fairly stable in pitch so trimmed ok (using altimeter) - i looked down at my GPS92 on moving map display and realised it could be used as a rudimentary wing leveler :-)
But then my philosophy from lesson 1 onwards has always been to use everything in the cockpit, can't understand those C150 drivers who think the AI is some sort of EFIS that one must go on training courses to understand...

[liam548]

back to the original post, I too remember this thread you are referring to, it wasnt that long ago it was active...
thought it might have been my post but not sure unti i look through it all


http://www.pprune.org/private-flying/349103-imc-ir-pilots-safer-3.html

[spekesoftly]

One of them was along the lines of 'trim to minimum speed and let go of the stick and keep the compass on heading with rudder' or some such thing.....
See this thread started by liam548, and third sentence of post #39 by Pace.

http://www.pprune.org/private-flying/352272-vmc-into-ifr-accidents.html

[bjornhall]

For hangar talk: Use the whiskey compass on a cardinal heading dealy...

In real life: Use the autopilot! :ok:

[1d2d3d4d]

What about a few hours IMC training?

Should cover straight n level, turns, stalls, descents, recovery from unusual attitudes, on full and partial panel and probably a cloud break procedure. Might be just more than a bit useful if you suddenly find yourself IMC!

Chris

[BackPacker]

Chris,

The OP was referring to a VFR-only aircraft and probably meant an aircraft with minimum equipment for VFR flight only.

Legal minimum would be a magnetic compass of some kind (whiskey or card), an altimeter and ASI. Maybe a clock or stopwatch but I can't see that being useful for inadvertent IMC. That's hardly what an IR pilot would call "partial panel" which assumes that either your AH or CDI is still working.

[liam548]

See this thread started by liam548, and third sentence of post #39 by Pace.

http://www.pprune.org/private-flying/352272-vmc-into-ifr-accidents.html

thats then one the post creator was referring to I am sure.

[Fuji Abound]

Jungle Drums

With, or without, an AI?

[bookworm]

Sometime ago on this site there was some talk about options that a VFR Only pilot in a VFR Only aircraft could use to descend to cloudbreak should they ever inadvertently become IMC without IFR training and equipment, or should everything become overwhelming.

This was the subject of the oft-misquoted "178 second" study by Jesse Stonecipher in 1956. The experiment took pilots with no instrument training, and tested what happened when they flew in simulated cloud (mean time to loss of control: 178 seconds). They then spent some time learning and practising the technique below. In the post-training set of tests, almost all successfully recovered. Note that this technique assumed no AI was available.

The technique used was:
Throughout, center the turn needle using the rudder.
1) Hands off the control column
2) Lower the landing gear
3) Reduce power
4) Set trim to a predetermined position for slow flight (95 mph) [this was a Bonanza]
5) Adjust prop and power for approx level flight at 95 mph
6) Note the compass heading
7) Turn using the rudder
8) Roll out with appropriate lead or lag
9) Center the turn needle
10) Reduce power for a controlled descent

[IO540]

That technique should work for any normal "IFR tourer" type. Most of them have a marginally positive roll stability for small deviations from horizontal, but they lack roll stability for large deviations which means this cannot be used for unusual attitude recovery in IMC ;)

If you find yourself in a 30-60 degree back in IMC and with no gyro instruments, all you can do is trim for some slow speed, shut the throttle, let everything hang out, and hope that you pop out of the clouds before hitting the ground...

[Fitter2]

The 'south heading' action using a magnetic compass was notably used by Anthony 'Bugs' Bendall to recover an early Lightning Mk1 with total electrical failure through about 20,000ft of cloud on asi and E2 standby compass only. He was a Master Green Instrument pilot, but does indicate that using the 'overswing without acceleration errors' effect works.

Australian pilots - use North heading.

Near the equator, I guess it doesn't matter..............

[1d2d3d4d]

BackPacker I might be a bit nieve here but surely most VFR only aircraft would have a turn and bank indicator! T&B, Altimeter & ASI will assist in straight and level, rate 1 turns and controlled descent, if you know where you are!

Chris

[jungle drums]

Thanks for all of your replies.

Yes, I was really talking about the case of a VFR pilot caught out without equipment, or even an IFR pilot in a basic IFR aircraft that has equipment problems.

The article referred to was super, and I have read the other link to post 39, but that wasn't it. But what you have all mentioned is roughly what was referred to in the original post if I recall correctly.

The original post had ppruners refer to latent aircraft stability, the analogy of a paper plane, and then the technique that you all mentioned was brought up - what struck me was the 'trim.........etc...... and let go', something that is going to be incredibly hard to do in the grip of fear.

I had intended to try it in visual conditions with a safety pilot to see how viable it was where things had already started to go pear shaped.

I think this is just a great tool in the toolkit to help save your life, and am shocked that I my toolkit was missing it.

[Croqueteer]

:ok:Nearly all a/c have at least one gyro, so try this. If caught in IMC and have to climb, Apply full power, fold arms across chest and using rudder only, keep the turn indicator central, or keep the horizon level, or keep the DI on a constant heading. You will not die (not just yet, anyway) To decend through IMC, heaven forbid, trim a/c to about 500ft/min decent and use same technique. Hopefully there will be a gap between cloud base and ground, or this will be the point at which you might die. Before commenting, go and try it!

[bookworm]

and then the technique that you all mentioned was brought up - what struck me was the 'trim.........etc...... and let go', something that is going to be incredibly hard to do in the grip of fear.

Indeed the Stonecipher paper remarks that the hardest aspect for the subject pilots was step 1 (Hands off the control column) even in the simulation.

If caught in IMC and have to climb, Apply full power, fold arms across chest and using rudder only, keep the turn indicator central, or keep the horizon level, or keep the DI on a constant heading.

What you write is correct, but it's worth bearing in mind that you don't always "have to climb". Climbing makes the aircraft less stable in roll -- a gentle descent is better if terrain permits.