F-86 and sound barrier

In article ,
Guy Alcala writes:
"Corey C. Jordan" wrote:

On 23 Sep 2003 07:47:41 -0700, (Walt BJ) wrote:

Exceeding M1.0 in either the Sabre or the Dog was no big deal. You
just pointed them straight down from 40+ and didn't fight it if it
wanted to roll around .95(flap rigging, usually).
Question: didn't Edwards get boomed when Welch went supersonic?
Walt BJ

It certainly did!

Prior to heading back to North American to debrief with the engineers, Welch
telephoned a friend that he had briefed the day before about what to be
listening for. Excitedly, his friend related that they had been nearly blown out
of bed by a terribly loud ba-boom. The time was noted and it corresponded to
George's dive.

Major General Joseph Swing heard the boom and reported it to Stu Symington.
Hundreds of others heard it too. Many wives ran outside looking for the
tell-tale plume of smoke indicating a crash, but there wasn't any smoke to see.

Ask any of the NAA guys (or the Bell crew as well) who were there at the time.
Welch's boom was quite loud, far more so than Yeagers would be (which makes
sense when you consider that Welch was diving towards the base, whereas Yeager
was in level flight at higher altitude).

Correct me if I'm wrong, but didn't the XP-86 still have the 4,000 lb. thrust J35C-3
at that time? Quite a ways down on thrust from the 5,200 lb. J47-13 of the F-86A,
and the top speed of the XP-86 in the only reference I have handy is given as 618
mph @ 14,000 ft. and 575 mph @ 35,000 ft. (M0.875), versus the 677 (presumably lower
down) of the F-86A. The XP-86 is credited in the same source with first exceeding
Mach 1 on 26 April 1948, but it's implied (not explicitly stated) that it did so on
a 3,920 lb. thrust J35-A-5, and that the J47 was first installed in the F-86A. This
seems more than a bit odd, to install an untried engine in the production a/c
without flying it in the prototype first.

The rather low thrust of the XP-86s is quite true, but in the case of
diving one through the Mach, it's pretty much irrelevant. The big
factor in barging into the region o rising drag isn't the 1,000-1,200#
of pusth that you're getting from the J35 at 40,000', bit the 13,000#
of gravity assist that you get in the dive. Of course, with such a
low thrust/weight, it took forever to get up there.

Roland Beamont made a "flying trip" to the U.S. in '47-'48 to assess
the various projects that were going on, and to get some first-hand
experience with American aircraft developments. (He flew the P-80A,
the P-84A, a B-45 prototype, and an XP-86) He did, in fact, make a
transonic dive in a J35 power XP-86. He did a series of article
about this trip, includig the flight test reports, in "Aeroplane" back
in 'bout 1988 or 1989. They were also chapters in "Testing the Early
Jets".

I've read pilot's accounts that say that some F-86As would 'hang up' and not quite
make it through the mach if you didn't do the roll in right, which suggests that the
XP-86 with its lower thrust might well have trouble. Of course, if exceeding mach
was mainly a question of drag rather than excess thrust, then it shouldn't have been
a major problem. I've just always wondered.

It's not so much a matter of thrust, as making sure you've got enough
dive angle on before you start getting into the thicker air below,
say, 20,000'. If you didn't get it pointed pretty much straight down,
you'd be running into thick air pretty fast.

--
Pete Stickney
A strong conviction that something must be done is the parent of many
bad measures. -- Daniel Webster