Scary story about landing on a Lake Tahoe golf course

Andreas Maurer wrote on 8/3/2020 5:34 PM:
On Sun, 2 Aug 2020 13:40:28 -0700, Eric Greenwell
wrote:

The tighter turn works for gliders after a rope break, so I'm thinking (as did
Paul B), it would work for the P51 pilot.

There is an optimum bank for minimizing the loss of altitude (and he did have some
altitude). Had he turned tighter (about 40 degrees typically), he would have made
it further around the turn than making a wide turn. Yes, initially he would be a
bit lower, but his greater turn rate would more than compensates for that, and he
can get back some of the that altitude when he stops turning and slows down.

Hi Eric,

From the video one can clearly see that his energy is barely enough to
cross the extended center line, including the flare. Definitely not
enough energy to make a turn, not to mention to drop the gear.


Let's do some maths:
When he started the turn to base leg he was between 250 and 350 ft AGL
(depending on his altimeter settings) and 150 mph.

P-51D stall speed clean: 100 mph, hence stall speed at 40 degreed
bank: 114 mph .

So, if he had flown a perfect approach at 120 MPH and 40 degrees of
bank, he would have had a turn diameter of 2305 ft, resulting in a
flight path distance of 3620 ft.

Having an altitude of 350 ft AGL, this would have needed an L/D of
10.3, with 250 ft he would have needed 14.5.

At 175 mph the L/D of the P-51D is 15:1, prop in high pitch. Close to
the stall speed L/D is an estimated 30 percent less, hence 10:1.
Propellor in low pitch will further reduce this number. I found no
numbers on the influence of open cooling flaps.
Let's assume an L/D of 10:1 for now (from the video probably a lot
lower).


Hence, the pilot might have had the chance to complete his turn if all
his factors had been in his favour, but even under these circulstances
he would not have had the energy to extend the gear. He didn't have
the altitude to extend it over the runway after the turn, and
extending it during the turn would have affected his L/D so much that
a crash was unavoidable.


If he had run out of energy (altitude and/or speed) in the last phase
of the turn, he would have definitely crashed, directly in front of
him the M-11 motorway, his flightpath still pointing at the thousands
of spectators. Hardly survivable.



Conclusion:
This landing is a perfect example of getting one's priorities right:

Fly the plane to a safe controlled landing instead of trying to get
back to the airfield, risking a probably deadly crash if only the
slightest thing goes wrong.



Two things
- you are supposed to fly the 40 degree turn at the minimum sink speed for that
bank angle, not near stall. So, the L/D would be significantly higher than 10
- I wasn't suggesting the tighter turn would be a better choice, only that it
would get him further around. Your answer may be what Paul B is looking for, as
the person who won

--
Eric Greenwell - Washington State, USA (change ".netto" to ".us" to email me)
- "A Guide to Self-Launching Sailplane Operation"
https://sites.google.com/site/motorg...ad-the-guide-1