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mad_jock
6th Nov 2005, 09:56
Moving on from this thread

http://www.pprune.org/forums/showthread.php?s=&threadid=197240

Thinking about it I have never been taught to recover from a spin on instruments. I was trying to think which ones would still work and also which ones could be giving duff information.

With a normal fit VFR aircraft what would you likely see and what would you look at to recover.

I have no problems spinning a tommy in VMC and have just realised that I never looked down at the instruments during a spin. Looked backwards once mind :D

MJ

DB6
6th Nov 2005, 11:07
If fitted, the turn needle will always indicate the direction of spin. Drill goes something like:
Check height (if parachute equipped), throttle closed, ailerons neutral, check turn needle and apply full opposite rudder. When needle comes off the stop centralise rudder and move stick forwards (or backwards if inverted) and recover from ensuing dive.
Altimeter, VSI (with lag), ASI and turn needle will work, not sure about turn coordinator as it may give duff gen when inverted.
Never tried myself and above is from (less than perfect) memory so others will know more.

Uncle Ginsters
6th Nov 2005, 13:21
If you end up in this predicament, you really ought to be asking some searching questions.....

The Standard Spin Recovery drill as taught by CFS (for RAF trg ac) is:
Check Ht (above Min Ht to commence Rec'y, MHCR)
Throttle Closed
Check Turn needle Direction
Apply full rudder to OPPOSE needle
Pause (for as long as it takes to say 'pause')
Control Column Centrally Fwd until spin stops
Centralise Rudder
Ease of of dive.

Know the spin recovery actions for your ac.

Some points to bear in mind:
- We use an MHCR of 3000agl+2000' and would abandon the ac if <MHCR in a VMC spin
- If IMC, then you're more than likely to be 'easing out of dive' on Limited Panel Instruments (as your Attitude Indicator/Artificial Horizon will almost certainly be toppled)

Not a nice situation to be in (just listen to that guy's voice!)- prevention is very definately better than cure - don't mess around in or near cloud if you're not suitably able to deal with all eventualities.

mad_jock
6th Nov 2005, 14:38
I agree prevention is better than cure and its not the sort of thing you want to go up and try.

What happens if you only have a turn coordinator? There pretty ****e for this sort of thing I seem to remember.


And the usual stuff if your a PPL reading the CFS method is for thier particular types. Read your POH and do what it tells you to do. As such there is no standard spin recovery.
If you shove the stick fully forward on some types all sorts of horrible things will happen.

BEagle
6th Nov 2005, 17:16
"As such there is no standard spin recovery"

Quite correct, mad_jock. More people need to remember that.

Throttle closed, ailerons neutral, check turn direction....THEN apply POH Spin Recovery Procedure!!

slim_slag
6th Nov 2005, 19:43
Depends on the cloud base.

orionsbelt
6th Nov 2005, 21:02
Instrument Spinning

Please note for information I relate my experience below, however do not try this exercise unless you are with a very experienced Aerobatic instructor in an appropriate aeroplane. (Suggest you see Alan Cassidy or his mates at EGLM )

Did some dual instrument spinning a few years back whilst learning aerobatics with an excellent (now retired) instructor.
In VMC and me using a IMC training hood.
For erect spins the Turn Indicator / Co-ordinator told the correct direction of spin whilst actually in spin and opposite rudder worked as defined. (We did not try inverted spins) As the spin stooped the indications changed but I cant remember what each instrument actually did but they were disconcerting and If I remember correctly you had to centralise rudder at different points depending if it was a turn indicator or a turn co-ordinator!

During the spin you must totally ignore the slip/skid ball, and treat the AH/DI as suspect, so you are recovering on limited panel.

If the spin was sustained for more that a couple of turns you experience (well I did )some massive sensory illusions and I had great difficulty recovering from the dive out. To the extent that initially I could not apply up elevator . You can end up going down very very fast and great care is required.

With the turn needle central you then had the problem of how to level out. So use the altimeter but ignore the VSI . Observe the rate of change of indication on the altimeter and as you climb it starts to slow so relax the back pressure. As you airspeed settles down with stable height apply S/L power and if you were trimmed for the S/L before you started the chance's are that you will be nearly S/L.

So in summary
On every spin I experienced sensory illusions which were overwhelming
You can end up going very fast straight down
I do not think I would have managed a safe recovery solo if below 3000ft we were loosing a lot of height.
Its not the best experience

One other point the Turn Indicator is subject to:-
Pitching Error;- occurs when a/c is yawing and subject to pitch up and will give an over reading.
Conversely will under read on nose down

Cheers Orion***

PS take a look at the Morning sky around 0500hrs from south to west
You will see: Saturn, Orion, The Pleiades and a fantastic Mars.

Uncle Ginsters
6th Nov 2005, 21:41
Slim_Slag,
Depends on the cloud base I hope you're not suggesting that you'd try IMC spinning given a certain cloudbase?:eek:
I have heard of an old IR examiner who would use a spin as an IF UP for experienced guys during tests - but even this was flown VMC and to the horror of most/all other examiners.
Definately not something i'd ever give an IR candidate on their rating:D ...on the rationale that any pilot who might accidentally enter a spin on instruments does not deserve a rating of any kind!

slim_slag
7th Nov 2005, 08:16
Not at all Uncle Ginster, in fact I wouldn't want to spin most aircraft in VMC. The topic is 'Dealing with an IMC spin'. My logic is that I just wouldn't fancy my chances of getting wings level after the gyros had had a few turns, and would prefer them to be level when pulling out of the ensuing dive. The spin is far friendlier to the airframe than a spiral dive, and if the bases are high enough I reckon I could recover visually with little problem. Didn't the original aviators deliberately spin through a cloud layer as they didn't have gyros?

hugh flung_dung
7th Nov 2005, 08:40
Ahem, I have a slight confession to make from a time long ago ...
We were looking at recoveries from developed erect spins in a Bulldog, above a hole in a fairly thick layer, and I inadvertently allowed the student to enter cloud during a spin - the recovery was standard but caused a certain amount of "mental focus" by yours truly. (Plainly a failure of the requirement for instructors to use their superior experience and judgement to avoid situations that require them to demonstrate their superior skill :) )

Afterwards I did a little practice under the hood and found that the difficult bit is the speed of response of the TI and being able to centre the rudder at the right time. The usual UP recovery on limited panel is to set power according to IAS trend, ball to centre, unload, roll until rate 1/3 indicated then centre ailerons, pitch until IAS trend reversal then check and adjust. I found that I had to use standard spin recovery to reverse the TI and get the IAS increasing and then use a standard UP recovery - but it's tough to believe the instruments after a multi-turn spin.

Another thought: knowing you are spinning is one thing but I should imagine that it would take a second or two to wake up to the fact that whilst in IMC you had entered a spin - not a pleasant situation and well worth avoiding.

In the dim distant past of my gliding days virtually all pilots were proficient at spin recoveries but not too hot at IF. It was normal to talk of "spinning down through layers" if anyone got caught on top because there was no chance of overspeeding whilst IMC - I never tried it.

HFD

FlyingForFun
8th Nov 2005, 10:07
I've always known that the (turn indicator/ball) works in the correct sense during any spin, and that the (ball/turn indicator) may work in the incorrect sense during an inverted spin.

Problem I have is remembering which is which! As MJ says, I've never looked at the instruments during a spin.

This thread has reminded me that it is the turn indicator which should be used to determing the spin direction. But does anyone have any mnemonics, or easy ways of remembering which is which, so that when the subject next comes up and I've completely forgotten this thread I will instantly know the answer without having to look it up again?

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

hugh flung_dung
8th Nov 2005, 11:12
FFF: The TI indicates rate of yaw whereas the ball will indicate centripetal force; the ball is useless in a spin. You don't need a mnenonic, just remember the standard spin recovery - especially the bit about "full rudder opposite to the turn indicator".

This is a bit worrying: I've never looked at the instruments during a spin - in an aggravated accidental spin you may not get the direction right just by looking over the nose - you MUST look at the TI and then apply the appropriate rudder.

A TI will indicate correctly whether inverted or erect but a TC will probably tell porkies when inverted because it's designed to be slightly sensitive to roll rather than just yaw. HTH

HFD

RodgerF
8th Nov 2005, 13:38
FFF

Looking at the instruments in the spin forms part of the spin demonstration and recovery patter.

"Notice the ASI is reading a low speed, the VSI indicates a rapid descent and the turn indicator shows (confirms) the direction of the spin" Then throttle closed, ailerons neutral etc etc

mad_jock
8th Nov 2005, 16:19
Well as an excuse for both myself and FFF. The JAR instructors course doesn't actually have spin pattering. You get made to do one in your test but you don't have to patter it. Its more to show you can recover from a student induced spin not actually teach it.
And i don't rememeber the instructor saying anything about Instruments. In fact there wasn't a TC or TI on the C152 I did my course on. Its not required for VFR flight.

As such the spin isn't taught any more since it was pulled from the PPL. And for some instrctors the first time they will be in a spin is on thier FIC.

Next question is why bother with a TC in light aircraft. Why not fit TI to them all.

hugh Flung_dung there is no such thing as a standard spin recovery

MJ

hugh flung_dung
8th Nov 2005, 21:41
MJ and BEagle: "there is no such thing as a standard spin recovery" - not quite true.
'Tis my understanding that, to be approved for deliberate spinning, an aircraft needs to recover within a specified number of turns "when the standard spin recovery" is used. The manufacturer may choose to publish a different spin recovery in the POH (which may give a faster recovery) but the aircraft is still required to recover with the standard spin recovery. Unfortunately I haven't got the references to hand, hopefully someone can post a quote - if not I'll dig them out ASAP.

(Edited 9/Nov: Quote from Darrol Stinton's Flying Qualities and Flight Testing of the Aeroplane, page 536: "When clearing an aeroplane for spinning, if the manufacturer's recommended recovery drill differs from the Standard Recovery Drill, then both are explored for the purpose of type certification. The reason is that pupils are taught the standard recovery drill in training. Under stress pilots often revert to earlier learned patterns of behaviour and, if caught out with an unexpected spin, many automatically use the Standard Recovery Drill without further thought".
The "Standard Recovery Drill" is defined on page 506, along with the recovery requirements.)

TCs give some response to roll therefore they react faster and supposedly make life easier when not spinning - nasty American invention ;)

HFD

A37575
9th Nov 2005, 09:56
This goes back a long way but I well recall spinning under the hood on Wirraways (Australian edition of the Harvard but more vicious wing drops).

Cage both AH and DG. Enter spin. After several turns (QFI said when) full opposite rudder and stick going forward. Concentrate on the Turn and Balance Indicator and watch for it to flick back through neutral (for want of a better term). Immediately the bat (of Bat and Ball genre) went through neutral, centralise the rudder and ease out of dive. You had to watch the Bat carefully while pulling out of dive, though - because if it still showed a slight rate of turn and you applied significant "G" the G force would act on the Bat and make it show a further rate of turn. So best to unload slightly during the pull-out if you suspected the Bat was misleading you. Keep Bat central during pull-out by use of appropriate aileron.

During the pull-out you kept a close eye on the ASI and as soon as it stopped increasing (from the recovery dive) you knew you were in level flight or close enough. Did several spins in Mustangs which wiped off lots of height, but fortunately never in IMC.

That was the beauty of the old fashioned Bat and Ball Indicator - (also known as Turn and Bank Indicator or Turn and Balance Indicator) it was practically fool-proof. Not so the Turn Coordinator which has an angled gyro wheel that can furnish erroneous indications if well beyond a rate one balanced turn.

The Turn-Coordinator I believe was never designed for anything but a rate one turn so relying on that for interpretation of spin direction and IMC recovery would be bad news.

I am only guessing now, but if by mis-chance I was in an IMC spin in an aircraft with a Turn Coordinator, then I would release all controls including rudder and hope that the aircraft would recover without my input. Some aircraft will do that providing you let go of the lot (don't forget to ensure throttle closed, of course) as soon as you realise you are are in an unusual attitude.

oldfella
9th Nov 2005, 22:35
The first problem would be to recognise that you are in a spin when IMC as opposed to a spiral dive (spin - low, possibly fluctuating IAS, spiral dive - high and possibly increasing IAS).

For an unusual position recovery, IMC, not spinning - The TI is affected by g so:

Speed / g / Roll / Pitch

Speed - Low or decreasing - select full power, high or increasing - select Idle power
G - unload (to give a reasonably correct TI reading
Roll - opposite to TI. As TI comes off the stops, centralise ailerons
Pitch - Opposite to Altimeter trend - as height change slows or stops, neutralise elevator.

You will be completely straight and level but fairly close. Disregard AH etc as gyros will probably have toppled., revert to limited panel then select cruise power and tweak roll and pitch to straight and level on limited panel.

If IAS is low and you suspect you are spinning you are in a stalled condition.

Power to idle.
Full opposite rudder to TI
Stick centrally forward until spin stops (TI will come off the stops).
Immediately centralise controls to prevent going in opposite direction.
Go straight into IMC UP recovery Speed / g / roll / pitch

Oktas8
10th Nov 2005, 06:33
The Turn-Coordinator I believe was never designed for anything but a rate one turn so relying on that for interpretation of spin direction and IMC recovery would be bad news. As a newcomer to this thread (but also as a spin instructor), I'm quite surprised by the distrust people have in the Turn Co-ordinator. I don't just want to pick on one individual's comment, but may I point out that the Turn Co-ordinator will indicate the direction of spin reliably in an erect spin? And in an inverted spin too in most cases. I'm quite surprised to read the opinion that a pilot might deliberately ignore the TC in a spin - what else will you use?

When easing out of the dive, I'd rather have a TC than a TI - according to my JAR ATPL notes it's less sensitive to looping error. Granted, it can't be calibrated accurately for rate 2+ turns, but how many civil pilots have a requirement for regular & accurate rate 2 turns?

Perhaps that's why light aircraft tend to be fitted with TC's not TI's. When I buy an aircraft approved for inverted spinning, maybe I'll have to go out and find an old TI to use instead...:ok:

Thanks for this topic mad_jock - it's very interesting!
O8

orionsbelt
10th Nov 2005, 14:30
Inverted spinning direction of Yaw and Roll

When you spin erect the direction of yaw and roll are the same. So the Turn Co-ordinator which responds to both yaw and roll will give an correct indication.

When you spin Inverted, the Yaw and roll are in opposite directions!

My inverted spinning experience has been on A/C fitted with a Turn Indicator which responds to yaw only, hence it tells the truth.

I do not know what a turn co-ordinator will indicate in an inverted spin.

The turn co-ordinator is designed to respond to both yaw and roll, that's why the Gyro is tilted at approx. 30 degrees up on the longitudinal axis.

The resultant forces acting on that gyro are going to be complex when spinning inverted and how that gyro will respond is beyond me. However I do suggest that we be very careful about speculating as to what it might or might not indicate.

Orions***

Centaurus
12th Nov 2005, 10:43
Turn Coordinators were originally designed looking like an artificial horizon so that if the VFR pilot inadvertently encountered IMC, in theory all he had to do was take his hands off the control column and use rudder to keep the "wings" of the TC level until he broke clear of cloud.

In discussing emergency operation in clouds, the C172 POH states: ..avoid overcontrolling, by keeping the hands off the control wheel as much as possible and steering only with rudder".

When the RAAF operated the CT4 trainer, the TC was removed and replaced with the standard bat and ball indicator which had indice marks for Rate One, Two, Three and Four turns - rather like the Tiger Moth Bat and Ball instrument. Spin recovery on instruments was more "natural" using the Bat and Ball rather than a turn coordinator.

Dan Winterland
13th Nov 2005, 01:05
The TC is a horrid instrument (IMHO), the design of which makes recovery from any unusual position (UP) difficult as it doesn't respond to g loading the same way as the TS. The gyro in a TC rotates the other way and under reads under loading as opposed to over reading as in the TS. My last flying club had the TCs removed from the PA28s and installed TSs for this reason.

In a previous life as an RAF QFI, we used to teach recovery from the spin on instruments during IF UPs. The standard UP recovery is to remove buffet, then roll the wings level, then pitch to the level attitude - all on the TS as the horizon had either toppled or it's failure had put you in the UP in the first place.

However, if you were in a spin the procedure was chaged. The first priority was to recognise you were in a spin - the definition of which is buffet accompanied by undemanded roll. In IMC, you can definately tell you have buffet, you can probably determine that you have undemanded roll too by your senses. The next step was to stop the yaw by putting the ball in the middle, then remove the buffet, then recover form the UP. Fairly straightforward, worked every time and our students had no problems coping with it.

However, as has been pointed out, the reovery techniques vary from aircraft to aircraft. This teqnique worked for the Chipmunk, Bulldog JP and Tucano (important to close the throttle on the Tuc though) but stopping the yaw and removing the buffet should work on most straight wing aircraft.

Also, I should mention that the CFI of the aforementioned club was BEagle!

Oktas8
13th Nov 2005, 03:47
Permission to go off topic briefly?

Centaurus - do you know why PAC put a spring coupling between the ailerons and rudder on the CT4? Not many manufacturers do so, and I'm quite curious.

mad_jock
13th Nov 2005, 10:22
Permission granted

The J32 had said spring link as well it was meant to help coordinate your turns and also had something to do with reducing the dutch roll with the yaw damper out or not fitted.

Oktas8
15th Nov 2005, 05:44
Thanks MJ!

I'm supposing that dutch roll is not a serious problem in a straight-winged aircraft designed for 120KTAS cruise at 5000' or so, and the only other reason I could come up with was the same as you did.

Seems odd for an air force basic trainer to have the coupling just to make it easier for the pilots to stay co-ordinated - I thought air force pilots were better than that...:E

Oktas

mad_jock
15th Nov 2005, 09:07
Well funny enough the J32 was a design for the RAF originally.