Unintentional Flight Into IMC.

[nevillestyke]

Yikes!
https://www.youtube.com/watch?v=8djWfNmJlKo&feature=youtu.be&fbclid=IwAR18c0ngrRorw1xkM14iTYe8p8l7z5vjDEyfy_QKsC7bTFcSS8M-n7GwW28

[Forfoxake]

Terrifying how quickly things go almost fatally wrong.

[Two's in]

Terrifying how quickly things go almost fatally wrong.


There was nothing "quick" about that little fiasco. That went wrong when either clown A or clown B decided to ignore: the NZ AIP, basic airmanship and meteorology for Dummies.

Very lucky to walk away from that, and scud running up a Cumulus bank is not "Clear of Cloud in sight of the surface"

[Big Pistons Forever]

The title of this thread should be corrected to Intentional flight into IMC......

[ShyTorque]

That was my own thought. There was an early option to turn right, away from the cloud and from the high ground.

[sycamore]

Feet seemed glued to the floor,slip-string all over the canopy......

[Pilot DAR]

Well two pilots made a remarkable poor decision!

Feet seemed glued to the floor,slip-string all over the canopy.....

Yes, I think I heard the word "spin" in there somewhere, hardly surprising! I can't see any mitigating factor to excuse entering the cloud as they did....

But, I credit them with posting the video, that others might learn.....

[ShyTorque]

From reading the comments under the video it appears that posting it in public was actually more unintentional than the IMC!

[rnzoli]

According to a video review of the incident, the most important mistake was to fly above the cloud layer, assuming that the positive vario they experienced on the windward side will remain. What probably happened - according to the reviewing glider instructor - was that as soon as they flew above the cloud layer on top of the ridge line, they lost situational awareness, got drifted over the ridgeline into the sinking air, and got sucked into the cloud layer. They weren't expecting this and tried to descend out at the bottom, resulting in a dive in the cloud and at least an 8 G pull-up when they saw the ground. There was no spin, it was more like a warning that they they might spin, if they continue to climb back into the cloud.

That useful video is removed now, possibly in an attempt to widthdraw the original one from public view.

[Less Hair]

Scary to look at. That's called instruction? Not many instruments for basic IMC flying are installed inside that cockpit.
Glad they survived it. Sharing it will help many others.

[blind pew]

GLIDING UK
It was relatively standard to have a turn and slip in UK gliders.
Cloud climbs not uncommon with a specific frequency to avoid collisions.
Climbed in cloud triggered by a coal fired power station with 5 others in an divergently unstable glider..not a problem bar the mental stress.
The video appears to illustrate what happens with wave flying whether the system is set up from terrain or wind shear.
Unfortunately the behaviour of the atmosphere isn’t predictable which caught these guys out...reminded me of what happened to the AirFrance guys penetrating the ITCZ.
Like many I have been caught out but remember gliding records are incredible..endurance 57 hours, altitude 60,000? and distance over 3,000 km. It’s what happens as do the accidents flying in the french alps.

[ShyTorque]

Cloud flying in good lift over a power station is one thing but I’ve never yet seen a coal fired power station sitting in the hills.

[tartare]

That is an utterly terrifying video to watch.
The initial flight into IMC is bad enough, but the footage of the trees and hillside - man, that could so easily have been the last thing they ever saw.

[Dan Winterland]

I was trying to read the g meter - it went to full deflection. 10g?

[Cornish Jack]

Two thoughts/questions - Was the altimeter set to QFE or QNH and, when faced with the cloud bank what prompted the turn to the left ('the valley') rather than the clear air to the right?
... a supplementary - Would pilots in a particularly mountainous country not have a grounding in the peculiarities of mountain flying and associated Wx effects?

[blind pew]

Basically NO.
I've been flying in mountains for 25 years after doing a unique weeks course with Jaques Noel who was the top professional mountain flying instructor. Part of every day was pointing out crash sites and how they got it wrong.
I am still learning about weather, orographic cloud, rotor and valley winds in spite of learning how to forecast 50 years ago and similar period observing from land, sea and air.
Altimeters are set to QNH for airspace and transiting goals between mountains. Displacement is purely on eyeball. Got caught out once as thought I was further away judging by the height of the fir trees until I could see the blades of grass having assumed that the trees were 60ft..in the upper slopes they are much shorter. The biggest danger in the french alps are wires followed by collision and lastly flying over colls where the air mass might be totally different and form a wall of cloud.
High G is used in gliders to avoid exceeding vne and flutter..used it once when low level aerobatics went wrong.
They are built far stronger than conventional aircraft..my first was tested to 12G.

[FullWings]

What he said ^^^

Having watched the video a few times, there’s nothing wrong with the skirting of the cloud initially, as they have a clear route out into a valley. One does wonder why they didn’t do some tacks in the lift to get above the cloud layer but I suppose that would have made it too easy.

When they turn left, it sets them up for a bad outcome, but they still had the ability to do a hard right and exit for quite a while. What I find incredible is that there don't appear to be any blind flying instruments in the front and judging by the unusual attitudes, in the rear as well. Even if they were in neutral air, it appears they would have gone into cloud, which leaves a huge ??? hanging over the whole thing. From the comments on the official NZ gliding site, it seem like one of those distracted instructor, unsure student scenarios where no-one really has projected the flight path forward.

If you’re going to flirt with cloud, you need a plan to get out of it, should the worst happen. Having some kind of reference is crucial as you will disorient pretty quickly, especially in turbulence. There are also occasions where, despite the best of planning, the weather changes and you have to do a cloud descent. If you don’t have any instruments, you can do it on GPS (or even a compass) but that requires a bit of skill and mental discipline. Better to have a phone app for emergencies - I use iBFD in case of a double failure in my panel.

[what next]

Hello!

Better to have a phone app for emergencies - I use iBFD in case of a double failure in my panel.

That's better than nothing, but don't forget that this is not a real artificial horizon. The effects of turbulence and prolonged turns will make it unreliable in less than a minute. It can help to maintain level flight for a very short while but not more than that. The solid state accelerometers built into smartphones are just that: accelerometers. Not real gyroscopes. And it needs to be turned on and "calibrated", i.e. aligned with the horizon, before it can be used.

[FullWings]

Not true for iPhones - they have all that’s necessary to create a full strapdown INS. I’ve had iBFD running for a whole flight including aeros and IMC and it was exactly in sync with my EFIS. That particular app I think was written by someone who writes software for instruments for a living and uses the gyros, accelerometers and GPS. If you don’t believe me, download it and try it - not expensive at £12. It’s not certified in any way but it’s better than a blank screen inside to go with the one outside!

I’m not suggesting for a minute that you should strap it to your yoke and take off in OVC000 and 75m but as something that is there for use in an emergency it could save your life...

[Big Pistons Forever]

The part I found profoundly sad was the “just another day in a glider” low key and low energy conversation in the cockpit. Where this video starts was in an area where great care needs to be taken. Not dangerous per se but there should have been a steady dialogue about how the situation was developing and where the out was as well as some definite “no go” criteria spoken out loud.

The huge one is never fly over a solid deck that is just below you and never ever ever be in a situation where up air is required to stay on top. This goes triple when flying over a ridge. Ridge cloud can develop and/or move very quickly with a change in wind and.has to be respected, as well as the absolute requirement to maintain positional awareness so that you don’t inadvertently cross over to the lee side and get into sink.

Frankly I wonder about the safety culture of this glider club. I find it hard to believe that given the relaxed atmosphere in the glider, that guys where not frequently pushing the ridge lift around and over clouds.

Google “Normalization of Deviance”

[blind pew]

It’s not unlike sailing when the conditions can change incredibly quickly especially in the English Channel where I have experienced force 7 or 8 when force 3 was forecast or an unforecast bank of thick fog in the middle of the shipping lanes. Are you suggesting that we should all give up and watch discovery channel.
I flew off a cliff two days ago, it took me an hour and a half to launch as the wind was too strong in the “compression” zone but once airborne I had a very enjoyable half hour. I had delayed two hours until there was enough beach to land on - 50% of water landings are fatal. And if the wind had strengthened there is a park in the lee after the main railway line.
It is about calculated risk as is wave flying when the slots in the wave bars can close in minutes and it was less than 25 years ago that we had a navigation aid that could give us a reliable position to allow a relatively safer decent in the mountains.
In my opinion my greatest risk is being maimed by some idiot on a mobile phone whilst walking the streets where a simple fall could be catastrophic.
As for safety culture..since when has shouting or a flustered high pitch voice been indicative of continuous risk assessment?
They got caught out as did AF447 and that lot were supposedly professionals, luckily they got away with it but were honest enough to post an embarrassing video so that others could learn.
To be fair unless one has experienced one of the engineless disciplines it is difficult to understand the mindset. Power flying involves a flurry of challenges and learning skills which quickly reaches a plateau and then becomes trying to reach perfection. Gliding can be a continual challenge of exploration with few infallible gurus to learn from.
At one time I used to attend a instructors two week camp auto towing of the beaches in Kerry with poor forecasts whilst attempting to use thermal, dynamic and wave lift in a mountainous region with ever changing cloud conditions. The site record was around 23,000ft by an ex RAF spitfire pilot.

[FullWings]

The part I found profoundly sad was the “just another day in a glider” low key and low energy conversation in the cockpit. Where this video starts was in an area where great care needs to be taken. Not dangerous per se but there should have been a steady dialogue about how the situation was developing and where the out was as well as some definite “no go” criteria spoken out loud.
I agree with that, especially in a “instructional” situation. I think neither pilot was planning far enough ahead, for whatever reason, as the end result shouldn’t have been surprising at all.

The huge one is never fly over a solid deck that is just below you and never ever ever be in a situation where up air is required to stay on top. This goes triple when flying over a ridge. Ridge cloud can develop and/or move very quickly with a change in wind and.has to be respected, as well as the absolute requirement to maintain positional awareness so that you don’t inadvertently cross over to the lee side and get into sink.
That is Ridge Soaring 1.01 - something we teach at our club to pre-solo pilots as there is a hill next to the airfield. How such a primal lesson got temporarily forgotten by experienced pilots in this case is interesting and it shows that distraction management is a necessary skill in any aircraft.

Frankly I wonder about the safety culture of this glider club. I find it hard to believe that given the relaxed atmosphere in the glider, that guys where not frequently pushing the ridge lift around and over clouds.

Google “Normalization of Deviance”
I suppose it was relaxed up to the point it wasn’t. Maybe neither pilot had had a “squeaky bum moment” in this environment, so although then knew “here be dragons”, they didn’t realise up to that point how large they were and how hot the fire was!

[Lookleft]

A couple of observations from the video. It was interesting how quickly the disorientation developed once they were fully in the cloud. I think they stalled because there appeared to be buffeting before it all went pear shaped. The other observation is that at no time did the instructor stop trying to fly the glider. There was certainly a high level of anxiety but there didn't seem to be uncontrolled panic. Going back to the start however there is no way the instructor should have allowed the situation to get that far. You are PIC at all times even if you are not manipulating the controls.

[Olympia463]

Who flies into IMC in a glider with NO turn and slip?? That pair must have been be mad as well as very lucky. I have flown a glider in cloud very occasionally but NEVER without a T/S. My most alarming trip was in my own glider which was fitted with an artificial horizon. Full of confidence I switched on the horizon and entered a large Cu at 4000ft and started to climb. At 8000ft things got very turbulent, and it seemed to be raining upwards, as the vario went on to its stop at +20kts. It took quite a while and another 2000ft to level the wings and fly out of the side of what was clearly a massive cloud. I LAFFT (I learned about flying from that). Did a nice cross country over the North York moors though.

The site I was flying from (Sutton Bank) had had a fatality earlier that year to a cloud flier whose plane disintegrated. I think that might have influenced my decision to leave while I was still ahead. I had some training in flying in cloud on the T/S alone in a two seater with an instructor, but it didn't really prepare me for that flight.

[FullWings]

I think that was what raised my eyebrows the most when watching the video. I’m guilty as charged in terms of IMC in gliders but at least I have the equipment and training that allow me to fly and navigate in those conditions. They appeared to have neither, which would make staying clear of cloud an absolute necessity which got overlooked somehow... :confused:

[jmmoric]

There's always the lack of instrumentation and all the other comments of what went wrong.

But a more practical question, since it's many many years ago I flew gliders (was 14 at the time).

In most small aircraft you can almost with certainty just let go of the controls and the wings should stay level and pitch would be according to trimming... so a hands off approach if in doubt should keep your head up.

The pilot in this film is kind of flying "gently", if it's not the pilot in the back controlling.... but would it have the same characteristics as a normal aircraft, or are they more unstable to begin with?

[Olympia463]

In a cloud a which is going up like a lift and bouncing you around, you would not expect releasing the controls to have a happy outcome. In clear non turbulent conditions I agree that you can let a well trimmed aeroplane fly itself, and when faced by a 'pudding stirring' pupil, it is often the only way to convince him/her that this plane can fly much better by itself. Having said that, it is a rare glider that is so well rigged that it does not enter a gentle banked turn after a short time. I suspect small single engined planes will do the same. But you are right, sometimes the best tactic is just to open the brakes,let go of everything and wait. Certainly the easiest way to recover from an 'unusual attitude'

[Pilot DAR]

I am not an experienced glider pilot, but I can say that few airplanes will find straight and level flight hands off in a useful way. I certainly would not think of letting go as a tool for when I upset the plane. Long period return to more level flight could involve an overspeed, or overshoot of the desired better attitude. It is simply the responsibility of the pilot to avoid flying into conditions for which the plane or their skills are not adequate.

This is the reason that some maneuvers are prohibited in some types, not that they cannot be flown, but the margin of recovery without exceeding a limitation is too small.

[Deltasierra010]

It’s that time of year, when experience pilots familiar with the local area, forget all their training and fly into hills.

It might have happened to me 4 yrs ago, I was passenger, we took off from Staverton and turned East , well clear of cloud, overhead the racecourse at around 800ft.
I said J*** turn North, - why, - we can’t see the ridge!. - oh :mad:
So we flew up to the army depot turned right and in the clear.

Orographic I guess, it was a straightforward VFR flight easy landmarks no particular plan.
We could easily have become a statistic that day

[nevillestyke]

A little more background here:
https://www.youtube.com/watch?v=NpyqiAp2TFY&feature=youtu.be

[Olympia463]

A little more background here:
https://www.youtube.com/watch?v=NpyqiAp2TFY&feature=youtu.be

And NOBODY so far (apart from me) noticed they did not have a turn and slip on the panel. What were they thinking about, going into cloud over a ridge on a turbulent day? You couldn't make it up!! If I was the CFI of the club concerned I would be standing that instructor down, and putting him in for a bit of training. What an example to a pupil! If they hadn't had a whole lot of luck they would have been another statistic.

What about the ANR's - you are supposed to keep clear of cloud and in sight of the ground at all times

Blimey!

[jmmoric]

Turn and slip indicator or turn coordinator is definately usefull, though I prefer the turn coordinator. An attitude indicator even better.

And don't call me NOBODY ;) (I did notice, and wrote it as well earlier)

[Olympia463]

Turn and slip indicator or turn coordinator is definately usefull, though I prefer the turn coordinator. An attitude indicator even better.

And don't call me NOBODY ;) (I did notice, and wrote it as well earlier)

And so you did. I apologise. It was disconcerting however to see so how many experienced pilots on this thread who missed this vital clue as to how these clowns got into that mess. I have flown twenty three types of glider in my career (now over) and never encountered one, all the way from T31 to ASK21, that was not equipped with a turn and slip. I thought perhaps I had missed it in my first scan of the panel - but no it wasn't there. I have to tell you that I would not have taken off in any glider not so equipped. I therefore never faced a decision about whether to enter cloud if it was necessary.

In my latter days of gliding I flew an Olympia 463 which (unusually for the time) was fitted with an HSI (why not just call it a horizon?) and while it was jolly useful in a cloud , should the battery have given out I still had the trusty steam driven T/S to save my bacon. Even when it seemed to be raining upwards in a cloud, a quick glance at the horizon made this unlilkely. The only thing a T/S could not tell you.

[arketip]

And NOBODY so far (apart from me) noticed they did not have a turn and slip on the panel. W

Not a glider pilot here, couple of questions.

- Do twin seater gliders have only one instrument panel?
- If they have two, can you confirm that this particular glider did not have a turn and slip in the aft panel?

Thanks

[Prop swinger]

This type has a panel for the back seat. There's no way of knowing what was fitted in it but it's unlikely there were any blind flying instruments, judging by the results.

[Prop swinger]

It was disconcerting however to see so how many experienced pilots on this thread who missed this vital clue as to how these clowns got into that mess. I have flown twenty three types of glider in my career (now over) and never encountered one, all the way from T31 to ASK21, that was not equipped with a turn and slip. I thought perhaps I had missed it in my first scan of the panel - but no it wasn't there. I have to tell you that I would not have taken off in any glider not so equipped.
The vast majority of gliders that I have flown were not fitted with a T&S & if I flew with one that was I usually wouldn't turn it on. It's not a required instrument if you remain VMC. The reason these guys got themselves in to that mess was that they committed the gliding cardinal sin of not having a Plan B (& C,D,E . . .) A working T&S might have been a Plan B but they would need to know what track they were flying, not easy with just a compass.

[Prop swinger]

I am not an experienced glider pilot, but I can say that few airplanes will find straight and level flight hands off in a useful way. I certainly would not think of letting go as a tool for when I upset the plane. Long period return to more level flight could involve an overspeed, or overshoot of the desired better attitude. It is simply the responsibility of the pilot to avoid flying into conditions for which the plane or their skills are not adequate.
To be certified for cloud flying (which this type is) the manufacturer must show that the type is speed limiting with full airbrake in a 45 degree dive. Gliders don't have the room for the full range of redundancy a certified IFR capable powered aircraft does. If you lose the instruments, or just lose it, the standard recovery (assuming that the glider was properly trimmed in the first place) is to open full airbrake and let go of the stick. The glider will eventually settle down in a speed limited low-ish G spiral dive. Not something I would want to do with the cloudbase so close to the ground but perfectly OK if you know you have the room.

[Olympia463]

Not a glider pilot here, couple of questions.

- Do twin seater gliders have only one instrument panel?
- If they have two, can you confirm that this particular glider did not have a turn and slip in the aft panel?

Thanks

Side by side two seaters have one panel - T21 and T42. Tandem two seaters - T31, Blanik, Bocian, K7, K13, ASK21 series german gliders etc, have panels in both cockpits. How else would you be able to teach people to fly? The panels are usually identical as regards instruments. I have flown about ten varieties of two seater in the UK, and all the tandem ones had full panels in both cockpits. Other countries might differ, though I can't think why.

[Andrewgr2]

Side by side two seaters have one panel - T21 and T42. Tandem two seaters - T31, Blanik, Bocian, K7, K13, ASK21 series german gliders etc, have panels in both cockpits. How else would you be able to teach people to fly? The panels are usually identical as regards instruments. I have flown about ten varieties of two seater in the UK, and all the tandem ones had full panels in both cockpits. Other countries might differ, though I can't think why.

The Bocian only has a panel in the front cockpit. The position of the rear seat might enable the instructor to see the panel in the front. Most 2 seaters I have flown in the UK have not had ‘full panels’. And the instruments in front and rear are rarely identical.

[megan]

was fitted with an HSI (why not just call it a horizon?)Have to be careful with terminology, HSI, a horizon it's not, i'm sure you mean AI (attitude indicator).


https://cimg8.ibsrv.net/gimg/pprune.org-vbulletin/206x204/usinghsi03_baea8ba4d6885b378d72014c14895644de6b501d.jpg

[Piper.Classique]

T21 and T42. Tandem two seaters - T31, Blanik, Bocian, K7, K13, ASK21 series german gliders etc, have panels in both cockpits. How else would you be able to teach people to fly?
same way that you do in a Piper Cub. Peer round the students head when you need to, otherwise fly the attitude. Most two seaters do have some sort of panel for the instructor, however. Not many countries allow gliders to cloud fly. France doesn't UK does as does Poland. And yes, I am a glider pilot, ex instructor on glider and power.
If cloud flying isn't legal then not much point fitting cloud flying instruments.

[blind pew]

That’s the problem..the mentality that if it’s illegal then don’t fit them, yet a parachute is mandatory in France! Flying comps in France you have to remove or blank the turn and slip...was it not a preworlds when Binder got caught out crossing a col and died when an attitude instrument could have prevented his death.

[Jump Complete]

That’s the problem..the mentality that if it’s illegal then don’t fit them, yet a parachute is mandatory in France! Flying comps in France you have to remove or blank the turn and slip...was it not a preworlds when Binder got caught out crossing a col and died when an attitude instrument could have prevented his death.

I’m really struggling with the thought process that prohibits a life-saving piece of equipment. Does everyone take the rule seriously (the having the instrument available bit, not the no cloud flying bit) it or just put a post-it note over the instrument and say “I promise not to be a naughty boy and take it off once airborne?”

[Prop swinger]

Same in US comps, I believe, & probably elsewhere. Blind flying instruments have to be removed or made inop. to prevent a competitor gaining an unfair advantage.

[blind pew]

Nope..had to be properly blanked so that it was impossible to use. Part of the problem is that the ffvl national centre is at St Aubin in the Alps Maritime, they have daily soundings and do not suffer the type of weather further north or closer to the Atlantic.
Running the worlds there gave the french team an unfair advantage.
plus ça change

[Olympia463]

same way that you do in a Piper Cub. Peer round the students head when you need to, otherwise fly the attitude. Most two seaters do have some sort of panel for the instructor, however. Not many countries allow gliders to cloud fly. France doesn't UK does as does Poland. And yes, I am a glider pilot, ex instructor on glider and power.
If cloud flying isn't legal then not much point fitting cloud flying instruments.
A reminder: this thread is about UNINTENDED flight into IMC. I agree that you might be able to teach flying by peering over someones shoulder but teaching correctly banked turns to a novice is easier if you have a T/S to show what is happening. A string might do the same of course but is not as good.

I don't know what the relevance of the French competition regulations is here!

[blind pew]

To become a world champion one needs to push one's limits which is what many pilots do in competitions and displays, a gyroscopic instrument is a safety factor like a parachute if it all goes wrong. Unfortunately one needs 3,000ft plus for a 50% chance of survival with a parachute.
I find it bemusing that an instructor needs the relevance of reducing safety pointing out.
The last french comp I attended as a spectator saw two fatalities and one broken glider on the airfield whose pilot tried to out run a sudden squall which reduced the visible to nearly zero.

[Piper.Classique]

​ teaching correctly banked turns to a novice is easier if you have a T/S to show​​​​​​
I don't think so, personally but that's not relevant to this discussion. Blind flying instruments are only a safety feature if the pilot is trained in their use. If cloud flying isn't legal then that would only be simulator training. You could argue that it was good enough but I would respectfully disagree. Proper training in cloud flying is an excellent thing, but no simulator available to a glidng club gives much idea of what its like inside a turbulent cloud. It's rough, wet, and can be thoroughly unpleasant. It's nothing like cruising a Pa28 between VORs or even flying a hold then an ILS. Speed limiting airbrakes make it less hairy, but these guys were flying a ridge, which put them pretty close to the terrain. Not a good place to go into cloud. More emphasis on not getting blown back into the sink would have been useful. The cloud certainly added another problem, but I suspect even without that they would have been struggling.



​​​​​

[blind pew]

Would disagree..in this case it was about heading into wind or away from the ridge with level wings in a trimmed glider. That sort of cloud is rarely turbulent or very wet..done that in both gliders and more difficult paragliders whose performance is affected by moisture and do not have the speed range. Have just bought an xc tracer maxx that not only has heading info but accelerometers giving wind, flarm, ground speed and position and can be tracked. Nothing like buying a bit of extra safety.

[blind pew]

Two decades ago I was slope/ wave soaring a slope in the lee of mount Brandon in Kerry around 400 ft agl in a phoebus C in which I had replaced the turn and slip with an ex RAF horizon and an inverter. To windward and below I saw a cloud forming so turned into wind and turned on the horizon. Unlike a turn indicator it was unusable for several minutes but fortunately I had a second generation gps which was fast enough to keep the wings level. I was engulfed in cloud within 30 seconds and briefly considered bailing out. A 360 would have seen me impacting the mountain.

[nevillestyke]

Nothing like buying a bit of extra safety.
I always feel that, as a paraglider pilot, the best bit of safety kit that you could get would be a hanglider.

[blind pew]

Would agree but I have enough problems at 71 hiking up a mountain with 15kg on my back and there is a slight logistical problem of getting back after an XC as even with an OAP bus pass I’m not so sure that a bus driver would let me take a hang glider with me..and taxis don’t have roof racks!
Now if we could wind the clock back to the good old days of the British Empire I could use a hangy wallah.

[Jim59]

Turn and slip indicator or turn coordinator is definately usefull, though I prefer the turn coordinator. An attitude indicator even better.

I agree that turn coordinators are preferable in most light areoplanes, where modest angles of bank are used in IMC. Thermalling in gliders, whether IMC or otherwise, involves angles of bank of 40 to 45 degrees where a T&S is a better instrument. My glider has both T&S and a horizon.