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How long can you fly by the seat of your pants IMC?



Caco

"How long can you fly by the seat of your pants" - but have you seen MY pants?

Boac wrote: ↑

Wed Jan 09, 2019 5:24 pm

"How long can you fly by the seat of your pants" - but have you seen MY pants?

That's is the perfect answer to my question. There's no answer to that!

Caco

This SACAA video narrated primarily by a senior ex-SAA Captain still chills me to the bone... and is a salient lesson to all pilots VFR or IR rated...



Caco

Cacophonix wrote: ↑

Wed Jan 09, 2019 5:13 pm

How long can you fly by the seat of your pants IMC?



Caco

Until I hit something.

Not long but just about the worst thing you can do is move your head, it topples the little position sensors in your ears but gravity will do that soon enough if you don't.

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I suspect there has been a significant change in training philosophy. Nearly fifty years ago when I first got my PPL in PNG, included were quite a few sessions of flying on instruments. These being provided on the basis that you're going to get caught out some day, so some basics could save your life. Whereas nowadays it may be considered unacceptable as it may be perceived as giving a pilot a false sense of security. So providing even a basic ability at being able to fly on instruments may be frowned upon.

When I went on to get an instrument rating with CPL, instrument training consisted of pulling down "window" shades, plus a shade between self and instructor, so as to preclude any possibility of external orientation. When NDB was the only nav aid available, doing a let down with no external references was as scary as ***** until you got the hang of it. But even then IFR in unpressurised aircraft within 50 nm of the mountains was expressly forbidden by the DCA. Flying in Papua New Guinea was a whole different ball game close to fifty years ago.

Alison

From the German Book of Der Fliegenvagen glossary:

VFR - lookinoutanseein fliegen
IFR - listenwaitinhopin fliegen

Quite accurate really.

Alisoncc wrote: ↑

Thu Jan 10, 2019 3:34 am

I suspect there has been a significant change in training philosophy. Nearly fifty years ago when I first got my PPL in PNG, included were quite a few sessions of flying on instruments. These being provided on the basis that you're going to get caught out some day, so some basics could save your life. Whereas nowadays it may be considered unacceptable as it may be perceived as giving a pilot a false sense of security. So providing even a basic ability at being able to fly on instruments may be frowned upon.

When I went on to get an instrument rating with CPL, instrument training consisted of pulling down "window" shades, plus a shade between self and instructor, so as to preclude any possibility of external orientation. When NDB was the only nav aid available, doing a let down with no external references was as scary as *sh*t* until you got the hang of it. But even then IFR in unpressurised aircraft within 50 nm of the mountains was expressly forbidden by the DCA. Flying in Papua New Guinea was a whole different ball game close to fifty years ago.

Alison

Still much the same Alison. Trouble is people let these skills atrophy, they forget the old lessons and they start taking risks, because all the electronics and gizmos available now blind them to those risks and then they do silly things like this...




Caco

Caco - yes, a worthwhile video.

Time to revive the old question which could just save your life - with only a magnetic compass, what heading would you choose to descend through cloud on?

Boac wrote: ↑

Thu Jan 10, 2019 8:48 am

Caco - yes, a worthwhile video.

Time to revive the old question which could just save your life - with only a magnetic compass, what heading would you choose to descend through cloud on?

That question is new one on me Boac. I am guessing that you might be alluding to one of the compass errors like acceleration error that is minimal on a northerly or southerly heading. I might try that so long as these headings were know not to be likely to lead to areas of high ground. I might also take up a known heading towards the coast where by judging distance by use of my estimated groundspeed (watch/airspeed indicator/estmiated wind speed and direction) I might attempt a let down over sea rather than over unknown topography.

Speak oh wise Sphinx, please enlighten the ignorant Caco!

Caco

Dig out your PPL notes, Sir. North would be a disaster, South will save your life.

PS Will not work with a gyro compass............................

Aiming for George, the option would have been to DR over the coast and let down over the sea. A bit more difficult at Inverness ('UK', for the Trumpsters...).

Does it make a difference as to whether you are above or below the equator Boac? And why?

Boac wrote: ↑

Thu Jan 10, 2019 9:39 am

Dig out your PPL notes, Sir. North would be a disaster, South will save your life.

PS Will not work with a gyro compass............................

Aiming for George, the option would have been to DR over the coast and let down over the sea. A bit more difficult at Inverness ('UK', for the Trumpsters...).

Ah well, I know Inverness well and have flown south east, VFR on top over Cairngorms from there before. I have also flown IFR over the same route in an aircraft not cleared for operation in known icing conditions and, surprise, surprise, started to picked up ice and just managed to make over in time to descend to wring the sweat out of my shirt!

Sigh, I am now rummaging through my dusty PPL notes.

Caco

Alisoncc wrote: ↑

Thu Jan 10, 2019 10:04 am

Does it make a difference as to whether you are above or below the equator Boac? And why?

I am guessing that in the Northern hemisphere you head due south because this has the least has compass error whilst turning? If you use this method you can focus on using the ailerons to just keep that heading and head on down. Of course if you did this from Inverness you'd go smack into the mountains.

Am I right oh Sphinx? Give me a heading to fly oh wise one!

Damn, the inscrutable one has departed to leave Caco to his miserable fate, lost in cloud over unknown terrain.


Caco

Of course, Alison - like bath water .................. Just perhaps, in view of our Southern Hemisphere readers, I should have mentioned that - but do we northerners care.................?

Thus for George ('SA' for the Trumpsters) you need to DR a bit further south!

Caco - just seen your latest
In the Northern hemisphere, heading magnetic south, ANY bank shows as a turn in the same direction. Thus keeping wings level is easier. Reverse all for heading north and for - the 'upside-down' folk.

Try it sometime.

Should also add that the effect is due (as you know!) to dip. Now, as usual, by going deeper into this we run into problems with the area the compass is built for - Southern Hemisphere compasses have different weighting on their needles to allow for the different dip, so my brain is hurting now thinking about flying a UK based a/c in Aus and trying to work out what happens on a northerly heading. I think the 'turning error' effect will be greater but I'll leave that to someone else.

Then there is what happens at the magnetic equator (where dip is zero) - time for Paracetamol.

Bring on duplicated IRS and GPS.......

Boac wrote: ↑

Thu Jan 10, 2019 10:26 am

Of course, Alison - like bath water .................. Just perhaps, in view of our Southern Hemisphere readers, I should have mentioned that - but do we northerners care.................?

Thus for George ('SA' for the Trumpsters) you need to DR a bit further south!

Caco - just seen your latest
In the Northern hemisphere, heading magnetic south, ANY bank shows as a turn in the same direction. Thus keeping wings level is easier. Reverse all for heading north and for - the 'upside-down' folk.

Try it sometime.

As yes, my notes indicate that compass indicated a turn in the right direction but occurring at a faster rate than is actually occurring.

Now that you mention this technique it comes back to me and I should have remembered it quicker as I read about it again recently. I am rummaging through my Kindle to remind myself where.

Many thanks for such an interesting point and the advice Boac.

Caco

Methinks I read it here... he used Boac's (aka the Sphinx) technique to save himself and the aircraft after a total electrical failure at altitude in cloud.

or in one of the many anecdotes in The Lighting Boys....

The story of Bendell destroying the glass in the control tower and showering his CO with dust etc. is hilarious.

https://www.ops-normal.org/viewtopic.ph ... ll#p149407

Caco

The question was:

How long can you fly by the seat of your pants IMC?

The old expression was "needle, ball and airspeed", I'm assuming by the question that you are taking away, at least, the needle and ball. So, you can have as many theoretical crew-room discussions as you like but they are unlikely to help you.

1. The human body and its balance mechanisms are designed to work in 2D not 3D so they are going to fail you and, at worst, actually mislead you.
2. IMC to an extent implies turbulence which I am guessing (not much IMC time in light aircraft) will cause any instrumentation you may have to be subject to lag and erratic indications.
3. Any turbulence will cause your bodies balance system to be further confused.
4. Any G-loading will cause your bodies balance system to be further confused which is why a smooth entry into a spiral descent is the usual result of loss of control in IMC.
5. The hangover which caused you to get into this situation won't help.

The first demonstration we carried out in the introduction to IFR flying was to blank off the students IFR visor and let him try to fly the aircraft by feel. Almost inevitably within a short time the result was an entry into a steep spiral dive which tightened up as the airspeed increased. You let the spiral dive wind up into a nice high-speed, increasing G descent, with your hands off the stick and then you told the student to pull up his IFR visor, when he saw the situation he was in he rapidly became a believer.


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