How to avoid CFIT
 

Hi All, I have often wondered what would be the quickest way to avoid an imminent CFIT, if all of a sudden a very large version of The White Cliffs of Dover comes into view. I have visited crash sites in the Berwyns, where WW2 aircraft have hit the mountains. Flying into a dead end valley is a known hazard.

When flying Indoor Models at Broughton, my favourite manoeuvre was to head for the wall, then at the last moment pull up and do a Rudder Stall Turn, to reverse direction. I could get very close to the wall that way, such that a highly banked turn would not have worked. I think that method only works because of adequate speed, and high G capability of models. So maybe it doesn't scale up to the full size aircraft.
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Would a tightly banked descending turn have worked with your model?
Most CFIT is in IMC, and you wouldn't be looking out the window, or aware of how far you are from other "walls".
In minimum VMC, at GA light aircraft speeds, you should have time to turn.
VMC CFIT is sometimes linked to downdrafts and turbulence. No precise manoeuvres will be possible in these conditions.

My instructor called that evasive maneuver a "Box Canyon Turn". Bank 90 degrees while pulling control yoke to stomach and praying earnestly to one's Maker! A fairly high-G aerobatic exercise, but our trusty 152 held together without complaint nor rippled sheet metal. It did take several hours for my internal organs to return to their normal positions after a half-hour of practice....

- Ed :ok:

Hi Maoraigh, Thanks for the reply. I think it is a bit of an energy management scenario, and the climb part is to reduce the speed and make any turn have less of a radius.
I think at cruise speed you would be below the Loop entry speed, so a half loop to roll-off at the top ( Immelman.) would be out of the question.
Maybe a pull up into a half Lazy-Eight, would give a tight turn around. I suppose it all depends upon your airplane type and your initial speed.
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An emergency landing before you get trapped seems to be a good procedure.See the AAIB links below. Manoeuvering in severe turbulence AND downdraft will not be in any way precise, and may overstress the airframe.

http://www.aaib.gov.uk/publications/...40__g_avwg.cfm
http://www.aaib.gov.uk/publications/...0m__n8174v.cfm
http://www.aaib.gov.uk/publications/...wk__g_bmvj.cfm
http://www.aaib.gov.uk/publications/...0h__g_awly.cfm
http://www.aaib.gov.uk/publications/...52__g_bilr.cfm
http://www.aaib.gov.uk/cms_resources...pdf_501881.pdf
http://www.aaib.gov.uk/publications/...2q__g_bmpo.cfm

I'm very concerned about where this thread is leading. There is no manoeuvre that will ensure terrain avoidance as described and to believe that there is is dangerous fantasie. Even if any terrain was to be avoided with an extreme manoeuvre, a loss of spacial awareness and control is sure to follow.

The only way to avoid terrain with certainty is to avoid it with a wide berth or by flying above it at a minimum safe altitude, whatever the flight conditions.

I'm just wondering - if I'm hammering down the motorway at 100mph in thick fog, and I suddenly want to avoid the stationary cars just ahead, am I best to try a handbrake turn, use cadence braking and prayer, or to steer violently towards the crash barrier, then try to catch the tail as it slides out by flooring the throttle and powering away? Or is this just a totally idiotic sort of 'Jet Blast' scifi nonsense idea?

I have tried it with my little RC toy car I Broughton ebuygum, and flicking it left works better than right, but I was wondering if it scales up to real cars. Can anyone tell me which I should try next time I'm unlucky enough to be caught doing a ton up in thick fog and everyone else has slowed right down in front?

Just askin'! Only sensible answers please...:ugh:

This, all of it.

Thanks for those reports Maoraigh, it sort of brings it home to you when one of the aircraft, BILR, was one of the first 152s I flew , when it was based at Sleap.

It seems that the downdraft situations play a big part in those accidents, not a factor I had to worry about when flying the models in the old De-Havilland Staff Dining Hall..!

Maoraigh has a lot of experience in flying around lumpy terrain and I have a little too, but I recall one flight North over the Grampians when the owner's voice from the rear seat of the Cub asked "why are we descending?" My reply, "because we can't outclimb the sink!"

He and I both knew one who died, along with his passenger, on a mountainside in poor weather probably due to downdraft on the lee side.

I would imagine the vast majority of CFIT is when the pilot cannot see the terrain... hence it's "controlled flight"... even in the model example, you have the luxury of being able to see the wall..

How to avoid CFIT? Avoid the situation that causes it... if vfr to imc, then turn arround. if ifr in imc, plan well.

If there's heavy fog on the motorway, do we still drive normally because we know how to do an emergency stop, or do we put a fog light on and slow down to avoid having to even need an emergency manoeuvre ?

It's all very well saying "I would not have started from here". IMHO it's worth the discussion. I would say that it depends on the information you have and what you can see, a violent turn or climb is probably worth a try.

"The only way to avoid terrain with certainty is to avoid it with a wide berth or by flying above it at a minimum safe altitude, whatever the flight conditions."
Flying at minimum safe altitude will not allow you to predict the downdrafts. Several accident reports show that. Few, if any, light aircraft can maintain altitude if unable to get out of the downdraft.
About 27 years ago a C177 was dragged down from a safe altitude above cloud, into the Cairngorms. They recognised the corrie they came out of cloud in. Before hitting the headwall they hit an updraft and were thrust back up clear of cloud. No damage so no AAIB report. Two very shaken guys turned back to Inverness. The wind forecast was OK when they took off.

Giving terrains a wide berth certainly works. But not everyone lives in flatlands.

Maoraigh seems to fly in the same area I do, and I am familiar with the challenges of doing so. Bottom line is, if you know what you're doing, its perfectly safe. If you don't... you are just inviting trouble on yourself.

How to avoid CFIT is simple... don't go grubbing about in marginal Wx especially near terrain, always have a plan B, C or D if the Wx turns for the worse, be aware and get educated on how to fly in and around mountainous terrain (pay attention to the forecast... where's the wind coming from and how strong is it, cloudbase, freezing level etc... check the terrain on your chart for your route, how will the wind interact with this? Wind stronger than 25Kt at mountain tops can cause problems if you are flying nearby. Etc.), and FFS don't fly for the sake of it! If things look iffy go another day.

Fly safe everyone.

I have very little experience of flying in mountainous areas and, when I have, I have always kept above MSA. However, doing some float plane training in Scotland I could see how one could become trapped in the "wrong" blind valley in VMC but finding the best climb rate is insufficient to clear the end of the valley. One would already be using best climb speed which would leave no spare energy for fancy maneuvering. If there is no room for a 180, the only option is to find the best ground to land on. I've done this sort of thing frequently on FS in places like British Columbia. FS gives you the extra option of instantly changing aircraft to one with a better ROC.:O

The scenario of blundering into a tight valley or other confined location in VMC (implying that you you had awareness of your proximity to the ground the whole time) is different from CFIT. CFIT suggests that you are flying in "cruise" flight, and for whatever reason, the ground suddenly surprises you (you didn't see it coming).

If you want to prevent a CFIT, either fly in sight of the ground, or fly IFR above minimum altitudes.

If you've blundered into a tight valley or similar, you did not think about you entered. If you're doing that at cruise speed, even dumber. If you are flying in terrain, and sudden or aggressive maneuvering may be required, fly more slowly, so you're slower than Va, and flap speed. This will increase your options for maneuvering. But hard maneuvering also greatly increases your risk of a stall spin, particularly if you pull G to do it.

I have trained many pilots to fly a canyon turn, usually on floats. Different aircraft fly canyon turns differently, so there is no one size fits all maneuver for this situation. But a key element is to avoid very sudden maneuvering, keeping things smooth, though unusual attitudes may be flown.

I don't deny that pilots get themselves caught in "terrain", and are unable to prevent crashing into it, but if they saw it, and maneuvered to avoid, it was not a CFIT.

Suddenly confronted with "dead end" terrain?

Two phrases come to mind:

1) A superior pilot is one who uses superior judgement to avoid having to use superior skills.

2) Proper prior planning prevents p!$$ poor performance.

There is a thread ongoing in Rumours and News about an airplane that was vectored by LAX ATC the wrong way, putting them towards Mount Wilson. If this was to ever happen in say a Norwegian Fjord, that would be another example of what could go wrong.

Obviously a heavy aircraft will not be able to out-manoeuvre a smaller GA aircraft, so the escape manoeuvres will need to be different. If the GPWS is triggered it will always offer the instruction.. 'Pull Up, Pull Up.', but that assumes that you have some excess energy available.

Scifi, you started this thread by presenting two possible escape manouvres, based on your experience with model aircraft. Please keep in mind that the power loading for a normal GA type aeroplane is vastly different from what you see with a model. Because of this, the available authority from, for example, the rudder is vastly different. And that's before we get into the available margins in the structure with regard to G-loading. All this will be worse if your trusty Cessna or Piper is loaded with a full set of adults and a bit of baggage. From straight and level flight at 100kt, you will be able to apply a fair bit of bank and pull the yoke into your gut, but that is the absolute limit of what I would attempt were I to be faced with a situation as you describe. The next thing I would notice would be the ASI needle heading towards the minimum value on the scale.

I concur with ShyTorque, keep those two phrases in mind at all times, thinking at least one problem ahead. I've been fortunate to have done most of my flying over a very flat landscape, and because of this I have absolutely no plans to venture into more rugged landscapes without a serious bit of preparation. I know that I'm not equipped for that kind of flying, so I either stay away from it or will take someone along who does know the gotchas.