Theoretical Situation: Forced approach and Nose over

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YCCA
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Re: Theoretical Situation: Forced approach and Nose over

Post by YCCA » Thu Jan 10, 2019 7:34 pm

Rich wrote:
Thu Jan 10, 2019 3:14 pm
YCCA wrote:
Wed Jan 09, 2019 7:40 pm
The key to doing this successfully would be absolute minimum airspeed and rate of descent, wings level, when the gear hits the water. I would do it in a normal landing attitude. I think the airplane would be less likely to flip nose over, then cartwheel, if you landed in a bank with one gear grabbing first..
I see this phrase about airspeed and ROD all the time. In a no-engine situation, these are mutually exclusive. Minimum sink speed is considerably north of stall speed.
I presume you land power off most every time so I’m not quite sure what you are saying? Point is you want wings, level, minimum rate of descent and minimum speed Aron touchdown. Wings level would be the number one priority to avoid cart wheeling
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Re: Theoretical Situation: Forced approach and Nose over

Post by Rich » Thu Jan 10, 2019 8:36 pm

YCCA wrote:
Thu Jan 10, 2019 7:34 pm
Rich wrote:
Thu Jan 10, 2019 3:14 pm
YCCA wrote:
Wed Jan 09, 2019 7:40 pm
The key to doing this successfully would be absolute minimum airspeed and rate of descent, wings level, when the gear hits the water. I would do it in a normal landing attitude. I think the airplane would be less likely to flip nose over, then cartwheel, if you landed in a bank with one gear grabbing first..
I see this phrase about airspeed and ROD all the time. In a no-engine situation, these are mutually exclusive. Minimum sink speed is considerably north of stall speed.
I presume you land power off most every time so I’m not quite sure what you are saying? Point is you want wings, level, minimum rate of descent and minimum speed Aron touchdown. Wings level would be the number one priority to avoid cart wheeling
This is true in a normal landing flare, where you dynamically bleed off speed in concert with judging height above touchdown, spending considerable time in ground effect. Into water you will often not be able to do this. That's mainly what I was referring to when I see this incompatible combination cited. I'm thinking into water I'm less concerned with vertical speed. It would seem to be advantageous to get the CG of the plane as low as you can as fast as possible to minimize the time span of high nose-over moment. Minimizing the deceleration forces and time by having a lower forward speed also works to this end. The footage of a Cirrus ditching a few years back enroute to Hawaii illustrates a useful boundary condition for reference. Lots of vertical speed and very little horizontal speed. (Probably not zero horizontal speed unless the surface ocean current and any local winds matched up perfectly). It doesn't appear minimizing sink rate has any real benefits in a water ditching. The insurance company owns the airplane, now, anyway.

If coming down on a decent landing surface presumably one tries something like a short-field landing technique, whatever that might be for the plane, and isn't that much out of the ordinary. Onto other hard-surface situations where a flare on landing is an iffy proposition. You do somehow want the best of both worlds. Too much ROD on the mains could produce a bounce causing loss of control. A long flare or ground roll increases the risk of maybe hitting a rock or stump or cow or ....

My normal final approaches are at a speed that's probably close to minimum sink rate (~60-ish KIAS). But touchdown tends to be about 40. Use of my GPS stuff could be helpful, also, to get a sense of which direction would produce a lower ground speed, though you don't want to get carried away. If you've been paying attention you probably already know this - it's something I cross-check pretty much all the time. The various EFIS gizmos that give you your current winds are an even more direct help than I have available.
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Re: Theoretical Situation: Forced approach and Nose over

Post by RMarkSampson » Fri Jan 11, 2019 1:09 am

Didn't that Cirrus ditching off Hawaii land under canopy - All vertical speed, near zero horizontal? Pilot is just a passenger at that point.
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Re: Theoretical Situation: Forced approach and Nose over

Post by Rich » Fri Jan 11, 2019 1:12 am

RMarkSampson wrote:
Fri Jan 11, 2019 1:09 am
Didn't that Cirrus ditching off Hawaii land under canopy - All vertical speed, near zero horizontal? Pilot is just a passenger at that point.
Correct. But my point is it lends support to the notion that vertical speed normal to the other axes (within limits) isn't something to worry about in a ditching.
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Re: Theoretical Situation: Forced approach and Nose over

Post by YCCA » Fri Jan 11, 2019 8:00 pm

Still not sure I follow ya, but I will say this.. We practiced this a lot when I flew P-3’s and the Navy has done extensive research into how to successfully ditch a plane. Wings level, minimum rate of descent of slowest practical speed, without stalling, are what they came up with. Granted in this scenario, you are power off but the same principles apply. Fly best glide to above the water surface, let the airspeed bleed off and touchdown with wings level in a normal to slightly higher than normal pitch attitude. In my opinion, that’s your best shot of walking, or should I say swimming away. I really hope none of us ever become the subject matter expert!!
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Re: Theoretical Situation: Forced approach and Nose over

Post by Rich » Fri Jan 11, 2019 9:12 pm

It's the "just above the water surface" that I'm assuming I can't rely on being able to judge properly, thereby running the risk of hitting the water with too much forward speed. Maybe way too much. So sometime on the way down I'm slowing to just above stall and don't worry about vertical speed at all.

I'm also not a slave to "best glide" speed, either. I don't see the value over water, especially, unless I'm trying to achieve some better spot on the water, such as closer to a ship or land, for example. Otherwise what does it get me? Even over land it's sometimes counterproductive.
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Re: Theoretical Situation: Forced approach and Nose over

Post by Steve » Fri Jan 11, 2019 9:20 pm

YCCA wrote:
Fri Jan 11, 2019 8:00 pm
We practiced this a lot when I flew P-3’s and the Navy has done extensive research into how to successfully ditch a plane. Wings level, minimum rate of descent of slowest practical speed, without stalling, are what they came up with. Granted in this scenario, you are power off but the same principles apply. Fly best glide to above the water surface, let the airspeed bleed off and touchdown with wings level in a normal to slightly higher than normal pitch attitude. In my opinion, that’s your best shot of walking, or should I say swimming away. I really hope none of us ever become the subject matter expert!!
Jeff: I also was in VP squadrons, back in the '80s. There have been a couple of successful P-3 ditchings that I recall. There was one in 1978 in the northern Pacific in horrendous weather, in which there was a failure to feather and a subsequent uncontained engine fire. About half of the crew survived the ditching and were eventually picked up by a Soviet trawler. Of interest, the PPC on that flight had extensive seaplane experience. I used to think about that one when we flew Red Route 20 out of Adak, and how long it took to put on those Imperial suits...

The only other one I am aware of was in the Med in the '90s, and I believe everyone survived that one. It was in much better conditions than the northern Pacific event.

Like I have said before, when I fly my single engine aircraft one water, I like to do it at sufficient altitude to make it to land if my engine bites the dust.

Steve
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Re: Theoretical Situation: Forced approach and Nose over

Post by YCCA » Fri Jan 11, 2019 10:59 pm

Rich wrote:
Fri Jan 11, 2019 9:12 pm
It's the "just above the water surface" that I'm assuming I can't rely on being able to judge properly, thereby running the risk of hitting the water with too much forward speed. Maybe way too much. So sometime on the way down I'm slowing to just above stall and don't worry about vertical speed at all.

I'm also not a slave to "best glide" speed, either. I don't see the value over water, especially, unless I'm trying to achieve some better spot on the water, such as closer to a ship or land, for example. Otherwise what does it get me? Even over land it's sometimes counterproductive.

I say go to best glide because if you stall it in, you die, every time. Yes judging height above water is tricky, but typically that is at altitudes of 100’ or greater where guys in parachutes released early.. My point is this.. Most of the guys flying a DA-20 have not practiced this kind of an emergency landing into water.. The more things you can keep the same, the better chance at survival. Best glide would give you some time above the water to get your wits about you and judge distance.. I’m not claiming to be the expert here, just using what I have learned over a career flying over water and giving my best advice as to how I would handle it... God forbid..
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Re: Theoretical Situation: Forced approach and Nose over

Post by Rich » Fri Jan 11, 2019 11:08 pm

YCCA wrote:
Fri Jan 11, 2019 10:59 pm
Rich wrote:
Fri Jan 11, 2019 9:12 pm
It's the "just above the water surface" that I'm assuming I can't rely on being able to judge properly, thereby running the risk of hitting the water with too much forward speed. Maybe way too much. So sometime on the way down I'm slowing to just above stall and don't worry about vertical speed at all.

I'm also not a slave to "best glide" speed, either. I don't see the value over water, especially, unless I'm trying to achieve some better spot on the water, such as closer to a ship or land, for example. Otherwise what does it get me? Even over land it's sometimes counterproductive.

I say go to best glide because if you stall it in, you die, every time. Yes judging height above water is tricky, but typically that is at altitudes of 100’ or greater where guys in parachutes released early.. My point is this.. Most of the guys flying a DA-20 have not practiced this kind of an emergency landing into water.. The more things you can keep the same, the better chance at survival. Best glide would give you some time above the water to get your wits about you and judge distance.. I’m not claiming to be the expert here, just using what I have learned over a career flying over water and giving my best advice as to how I would handle it... God forbid..
Minimum sink speed (not best glide) is what gives you the most time to "get your wits about you". And it's typically considerably slower than best glide. For my typical flying weight best glide runs just under 70 KIAS. Minimum sink is around 60. This is actually my normal over-the-fence speed and is a good hedge against low-level loss of headwind. Last year I was doing a demo engine-out landing during a BFR. I had some traffic to contend with and lurked about at this latter speed waiting for it to clear before turning in to the airport. It felt like I had all day to watch the activity resolve itself.
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Re: Theoretical Situation: Forced approach and Nose over

Post by Rich » Sat Jan 12, 2019 12:07 am

Steve wrote:
Fri Jan 11, 2019 9:20 pm
Like I have said before, when I fly my single engine aircraft one water, I like to do it at sufficient altitude to make it to land if my engine bites the dust.

Steve
I spent a number of years flying over Puget Sound. There are times/places when the water is a more attractive option than trying to reach the adjacent land. And there are windows of vulnerability (usually right after takeoff) where engine loss means you're going into the drink.

This fatal accident was the result of gliding in over the water only to hit a bluff on Whidbey Island.

https://app.ntsb.gov/pdfgenerator/Repor ... L&IType=FA
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