flight support aircraft - Cape to Cairo Challenge RIP

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Mrb13676
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Re: flight support aircraft - Cape to Cairo Challenge RIP

Unread post by Mrb13676 » Tue Aug 06, 2019 12:34 pm

Dragon wrote:
Tue Aug 06, 2019 11:40 am
Mrb13676 wrote:
Tue Aug 06, 2019 7:28 am

The transition from Vx to VbestGlide in my Sling 4 is pretty hectic. It needs a MASSIVE push and is very unpleasant. FWIW I never climb at Vx routinely for this reason.
I haven’t flown a Sling, when you say “MASSIVE push and is very unpleasant”, do you mean:
a) travel forwards of the stick is an uncomfortably large distance?
b) stick force is unpleasantly high?
c) it is a sustained manoeuvre and you find the zero G unpleasant?
I am trying to work out whether your experiences are traits unique to the Sling or are what we usually experience during this manoeuvre.

(as an aside I have a sneaky suspicion in a few posts time I will find myself once again recommending gliding training to all, during which this manoeuvre is practiced countless times during the winch cable break procedure)
I’m guessing the experience is the same on most aircraft. There seems to be quite a change in attitude which causes a lot of Zero G. I find it worse on the Sling than on the Cirrus. But those are the only types I have flown so I can’t comment.
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Re: flight support aircraft - Cape to Cairo Challenge RIP

Unread post by Dragon » Tue Aug 06, 2019 12:37 pm

PJL wrote:
Tue Aug 06, 2019 8:52 am
No problem Mike, I have never flown a Sling 4 but I am concerned that the aircraft could have insufficient power in an emergency when it is heavily loaded let alone a total engine failure. Please I am not knocking the aircraft but just expressing my opinion. I fly a RV10 and if you get behind the speed curve she drops out the sky like a brick. BTW my initial comment was also quickly/poorly constructed but there is a huge chance that a stall occured with tragic results, again this MY opinion.
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There are some very interesting and important concepts here. We know the aircraft was heavy and the excess power was low so it’s performance with power would have been very limited, I think that’s a given for a flight of that nature.

What is interesting is the gliding performance. Few people know that the gliding performance (measured in glide ratio ie distance - not endurance) of a heavy aircraft is surprisingly similar to a light aircraft. This is because glide is primarily dependent on lift to drag ratio. Now you do need more lift in a heavier aircraft to compensate for the heavier weight, but all you do is increase speed as per lift formula, until your glide is almost as good as it should be. There is a small loss of performance because although as you move away from the induced drag of low speed things improve, you unfortunately start to pick up more and more parasite drag from high speed, and this is the tax you pay, but it is small. And this is how gliders get away with flying around voluntarily carrying water in their wings. So if your aircraft is carrying more cargo or fuel, best glide will need to be faster, which means more effort diving to get to that speed BUT once you have obtained it your glide performance is thumbsuck 95% as good as the unloaded aircraft. Just be aware that your turn radius is bigger, and importantly that your stall speed is higher. Your rate of descent is also higher but you are going further because your glide ratio is similar, it’s just that everything is happening quicker. Also If you don’t get the speed up, you will indeed sit behind the drag curve and glide like a brick. Unfortunately a heavy aircraft does not help you with glide endurance if you are playing for time and not distance- you are going down quickly whether you do at at high IAS or at low IAS.

So the question is did they know all the repercussions of a heavy aircraft, the adjusted stall speed etc? Knowing Des I am sure they did. Did it bite them? Now that is a different question. Des was extremely experienced and an outstanding pilot, but let us never forget that he was human just as we are. Only time will tell.
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Re: flight support aircraft - Cape to Cairo Challenge RIP

Unread post by jimdavis » Tue Aug 06, 2019 1:12 pm

Mike, your talk of MASSIVE push on the stick and prolonged zero G are a bit alarming in that they sound like panic reactions rather than smooth controlled flight. Certainly one must react immediately and positively in order to get the aircraft gliding at the best speed with minimum height loss.

Perhaps it's the zero G that worries me. Even a short period of zero G can cause a power loss through fuel lifting in the float chambers of carburettor engines, and fuel unporting in the tanks in any aircraft.

My thought is that if the aircraft was really heavy it would have had a very poor angle of climb and would still have been low when the engine lost power. This would leave them with little height to manoeuvre. They may have stalled, or simply landed sufficiently hard to rupture a tank.

A very nasty situation form which even the best of pilots would have has no back doors.

jim
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Re: flight support aircraft - Cape to Cairo Challenge RIP

Unread post by HJK 414 » Tue Aug 06, 2019 1:31 pm

jimdavis wrote:
Tue Aug 06, 2019 1:12 pm
……...
My thought is that if the aircraft was really heavy it would have had a very poor angle of climb and would still have been low when the engine lost power. This would leave them with little height to manoeuvre. They may have stalled, or simply landed sufficiently hard to rupture a tank.
……….
jim

Jim,

If you look at this photo - the debris field is all to the right of the engine block.(which you see the bottom of in earlier pics)
Only the wheel is on the left.


Pancake 1.jpg


It suggest that the aircraft went in on it's right hand side and had very little forward velocity (no apparent skid marks) when it impacted.
In my view - they lost airspeed - the aircraft banked right and they impacted with the right wing (almost pancake style) and the fuel in that wing did the rest.

JK
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Re: flight support aircraft - Cape to Cairo Challenge RIP

Unread post by mnmodels » Tue Aug 06, 2019 1:42 pm

jimdavis wrote:
Tue Aug 06, 2019 1:12 pm
A very nasty situation form which even the best of pilots would have has no back doors.

jim
Very interresting statement uncle Jim. So lets get back to basics. The PIC is in control of the flight and did the planning and the W&B. If the PIC find that an engine failure between point A and B leaves no back door....does he go ahead with flight?

Or does the back door concept go out the door with the more experience you have....just a question that comes to mind reading the post....

No direspect to the the pilots as we do not know the facts yet - just an observation in general.
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Re: flight support aircraft - Cape to Cairo Challenge RIP

Unread post by Mrb13676 » Tue Aug 06, 2019 2:05 pm

Jim, there is a lot of stick travel so it feels like a big push. It is by no means HARD to push. I suspect that any period of zero G feels like a long time to those of us unused to it. I would be interested to know if the period of zero G is enough to interrupt carb fuel flow, I’ve certainly never seen any hesitation in the pushovers I’ve done in practice. And I agree, the instinct is probably one of panic because no matter how hard you train the actual event is going to make you wish for a new pair of underwear.

[pure speculation]
I had a look at the W/B for the Sling - with two 70kg pilots, full fuel in the wings, you can put 150kg in the back before being out of the envelope - 210 odd litres of Mogas. This aircraft has been flown at around 50% above MAUW on the RTW trip, so one wonders how much fuel WAS on board and how out of envelope the aircraft may have been? (If in fact the theory of ferry fuel is true - we have no confirmation as yet.) It may have been very difficult to get the nose over when/if the donkey quit...
[/pure speculation]
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Re: flight support aircraft - Cape to Cairo Challenge RIP

Unread post by GL » Tue Aug 06, 2019 2:18 pm

As I said earlier:
GL wrote:
Mon Aug 05, 2019 10:46 am
--- the thing that often surprises pilots used to flying heavier aircraft is the lack of momentum in light sport aircraft. When you cut the power they just about stop dead in the sky. You need to get the nose down IMMEDIATELY.
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Re: flight support aircraft - Cape to Cairo Challenge RIP

Unread post by bosvark » Tue Aug 06, 2019 2:39 pm

mnmodels wrote:
Tue Aug 06, 2019 1:42 pm
jimdavis wrote:
Tue Aug 06, 2019 1:12 pm
A very nasty situation form which even the best of pilots would have has no back doors.

jim
Very interresting statement uncle Jim. So lets get back to basics. The PIC is in control of the flight and did the planning and the W&B. If the PIC find that an engine failure between point A and B leaves no back door....does he go ahead with flight?

Or does the back door concept go out the door with the more experience you have....just a question that comes to mind reading the post....

No direspect to the the pilots as we do not know the facts yet - just an observation in general.
I unfortunately have no piloting experience :( but won't many flights at some stage be in a position where you may not have any "back door"? If so then much less flights will actually take place? Flying out of some places for instance have basically no place to put a plane down in an EFATO (developed areas for instance), so no "back door" really.
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Re: flight support aircraft - Cape to Cairo Challenge RIP

Unread post by SimplyFly » Tue Aug 06, 2019 2:47 pm

Dragon wrote:
Tue Aug 06, 2019 11:40 am
I have a sneaky suspicion in a few posts time I will find myself once again recommending gliding training to all, during which this manoeuvre is practiced countless times during the winch cable break procedure.
You are reading my mind, Dragon. In gliding the standard teaching for a cable break goes something like:
* Release, release. (Immediately, with left hand. In case a hundred kg of cable is dangling below the glider.)
* Nose down to flying attitude (just as immediately, at the time, with the right hand. So far it takes about 2 sec. It is quite possible to get dirt from floor in your face.)
* Confirm flying speed is achieved. (Only another few seconds)
* Only then work on your landing options.

This avoids turning before the speed is established.

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Re: flight support aircraft - Cape to Cairo Challenge RIP

Unread post by jimdavis » Tue Aug 06, 2019 3:28 pm

mnmodels wrote:
Tue Aug 06, 2019 1:42 pm
jimdavis wrote:
Tue Aug 06, 2019 1:12 pm
A very nasty situation form which even the best of pilots would have has no back doors.

jim
Very interresting statement uncle Jim. So lets get back to basics. The PIC is in control of the flight and did the planning and the W&B. If the PIC find that an engine failure between point A and B leaves no back door....does he go ahead with flight?

Or does the back door concept go out the door with the more experience you have....just a question that comes to mind reading the post....

No direspect to the the pilots as we do not know the facts yet - just an observation in general.
Most takeoffs in a light single leave you with either no back door, or a very small one. I was suggesting that, in general, an experienced pilot will have a better chance of surviving an EFATO, than a low hour one. But many very experienced pilots have died trying to turn back. I have no idea whether that is the case with the poor people.

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Re: flight support aircraft - Cape to Cairo Challenge RIP

Unread post by jimdavis » Tue Aug 06, 2019 3:41 pm

Mrb13676 wrote:
Tue Aug 06, 2019 2:05 pm
Jim, there is a lot of stick travel so it feels like a big push. It is by no means HARD to push. I suspect that any period of zero G feels like a long time to those of us unused to it. I would be interested to know if the period of zero G is enough to interrupt carb fuel flow, I’ve certainly never seen any hesitation in the pushovers I’ve done in practice. And I agree, the instinct is probably one of panic because no matter how hard you train the actual event is going to make you wish for a new pair of underwear.

[pure speculation]
Perhaps we are splitting a very fine hair. The difference between zero G and a touch of negative G is minuscule. Perhaps your practice 'pushovers' were not sufficient to lift the fuel in the float chamber, but I can assure when you do aerobatics with a carburettor engine you expect the power to die during even short periods of slightly negative G.

BTW you mention practicing 'pushovers'. I am not sure what you mean - what are they for? And do you practice them with power, or while throttled fully back?

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Re: flight support aircraft - Cape to Cairo Challenge RIP

Unread post by Mrb13676 » Tue Aug 06, 2019 4:31 pm

jimdavis wrote:
Tue Aug 06, 2019 3:41 pm

BTW you mention practicing 'pushovers'. I am not sure what you mean - what are they for? And do you practice them with power, or while throttled fully back?

jim
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Re: flight support aircraft - Cape to Cairo Challenge RIP

Unread post by Volo » Tue Aug 06, 2019 5:28 pm

I somehow don't think the aircraft Spun in as has been postulated by some - The spinner is in to good a shape for that . Most spins from low level would initially be by and large vertical .
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Re: flight support aircraft - Cape to Cairo Challenge RIP

Unread post by Chalkie » Tue Aug 06, 2019 5:36 pm

Mrb13676 wrote:
Tue Aug 06, 2019 2:05 pm
[pure speculation]
I had a look at the W/B for the Sling - with two 70kg pilots, full fuel in the wings, you can put 150kg in the back before being out of the envelope - 210 odd litres of Mogas. This aircraft has been flown at around 50% above MAUW on the RTW trip, so one wonders how much fuel WAS on board and how out of envelope the aircraft may have been? (If in fact the theory of ferry fuel is true - we have no confirmation as yet.) It may have been very difficult to get the nose over when/if the donkey quit...
[/pure speculation]
Any aft CG condition would make an aircraft pitch sensitive, so "getting the nose over" would be easy.
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Re: flight support aircraft - Cape to Cairo Challenge RIP

Unread post by frikie » Tue Aug 06, 2019 5:58 pm

Hi Jim.

I only have experience on the sling 2. They are extremely easy to fly and the "push" is no more of a "push" or negative g than what you experienced in your career I'm sure. I would rather say that it is a matter of immediately pitching the nose towards the undercarriage. I would not think that the Sling 4 would be any different.

Regards

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