More useless stuff....

[Britbrat]

I'm not sure that I accept the argument of the F-86 exceeding Mach 1 prior to the X-1. Shortly before Yeager & the X-1 oficially did the deed, a British test pilot on an exchange visit was the first to nominally exceeded Mach 1 on the F-86's machmeter, however, there was no associated sonic boom. Nor were there any other documented instances when a sonic boom was heard prior to the X-1's big day.

Interestingly, the highest ever Mach no. achieved prior to the appearance of F-86, was 0.9, by a Spit Mk XI in 1944, in a formal comparison with a P-51D and P-47D.

[Wayne]

and a little putty knife deploys to scrape the crews' faces off the windscreen. (The stopping power is pretty dramatic.)

...nice touch Boeing thinks of everything, don't they??

[Galvin]

I am perfectly able to accept the idea of the sound barrier being broken by the XP-86 prior to the X-1. The simple reason for that belief is that it was undergoing test flying at the time and that F-86s are able to exceed the sound barrier in a shallow dive has been proved countless times since.

The fact that no record exists of a sonic boom is to me not a reason to disbelive it. Given the absolute control the military had on relevant information at the time (absent the broadcasting of the feat by the aforementioned exchange Brit, a breach of secrecy that drove the USAF up the wall) I have little doubt that it happened.

I think the Air Force was well aware that the XP-86 had done the deed first but were loath to make the admission lest the X-1 program be threatened. I imagine what they must have thought at the time. If we had a production aircraft that could exceed Mach 1 then why were we screwing around with a straight-winged, rocket powered experimental aircraft that had to be airlifted to altitude, of inferior aerodyamics, and completely impractical to convert to production?

The North American test pilot George "Wheaties" Welch had been complaining that the airspeed and altimeter were fluctuating unusually and indicating Mach 1 at the pitot head and so the engineers decided to find out why. Since they had no means of calibrating air speed indicators into the transonic range at the time, they received permission to use the same tracking theodolite and large radar dish that had been used to track Yeager's Mach 1 flight five days earlier (October 14, 1947) in order to determine the true speeds the XP-86 had been achieving up to that time.

The theodolite was coupled with a very accurate tracking radar and profiles were flown to duplicate the conditions that were causing the instrument fluctuations that Welch had been complaining about. The engineers were shocked and delighted to find that they got readings of Mach 1.02 and 1.03 on the two runs through the system, speeds the XP-86 had already reached many times prior to the X-1s "historic" flight.

Given that the instrument fluctuations were determined to be occurring at speeds recorded on the theodolite/radar course as exceeding Mach 1 and that those fluctuations had been documented as an instrument problem for weeks prior to Yeager's flight, there is little doubt that the XP-86 was the first through the sound barrier, boom or no boom being recorded.

As in the case of the people involved in the X-1 (or more correctly , XS-1) program, everyone in the XP-86 test program was immediately sworn to secrecy and the details of the flights did not emerge for many years.

The U.S.A.F. had just become an independent branch of the armed services and Stuart Symington had been sworn in as the first Secretary of the Air force. He called North American's Dutch Kindelburger and ordered him not to admit that the XP-86 had gone past Mach .935.

His motives for issuing this order are not known but funding of the XS-1 program and the Air Force's not losing face or credibility with those who had secretly been told of the breaking of the sound barrier by the XS-1 come to mind. Apparently the Air Force did not wish to admit either that it wasn't one of their pilots but a civilian test pilot who was the first.

Interestingly, all the above XP-86 flights, including through the sound barrier, were accomplished with the original 4000 lb thrust GE J-35 engine. It was later re-engined with the 5000 lb thrust GE J-47, the engine that powered the production airplanes.

The fact that the XP-86 and later the F-86 could easily exceed the sound barrier and had in fact almost certainly done so prior to Yeager's flight remained officially secret even though the 14 June 1948 issue of Aviation Week (Sometimes called Aviation Leak to those in the know) announced that the XP-86 had gone supersonic. A lot of people knew it anyway because of the following incident but the magazine made it official.

On April 26, 1948 a visiting British test pilot was checked out in the XP-86 and, despite being briefed on the ability of the aircraft to exceed Mach 1 and the strict security surrounding that fact, managed to broadcast his feat of going through the sound barrier in the XP-86 to every tower in line of sight through the oversight of transmitting his comments on an open radio channel. He was severely chewed out for it but the secret was a secret no longer.

BTW: The 35 degree swept wing on the F-86 was based on captured German data for a proposal to put a more sharply swept wing on the Me-262. The instability problems of swept wings at high angles of attack, particularly during landing, were to be overcome by the use of leading edge slats and North American adopted this solution as well.

It is a little known fact that the leading edge slat tracks on the wing of the F-86 were slightly modified copies of those on the Me-262. Instead of manually cranking them out as the 262 required, they utilized the movement of the airflow stagnation point (the point on the leading edge where the airflow divides to go either over or under the wing) to operate the slats automatically when higher angles of attack get the stagnation point into the slat/wing gap and forces them open.

The slat lock and control switch on the XP-86 was cannabalized from an Me-262 and the tracks were modified from captured Me-262 units. In fact, the first seven production aircraft had slat locks and modified slat guide tracks taken from captured Me-262s.

[Britbrat]

Very interesting & comprehensive information, however, the XP-86 & early production Sabres were not capable of "easily exceeding Mach 1" -- the early versions did so in full-throttle vertical dives from high altitude, and frequently were not successfull in exceeding Mach 1 before their speed fell off at ~ 20, 000 ft. Later, much more powerfull varients, were capable of exceeding Mach1 in a 45 deg dive from 40,000 ft. Even the hottest F-86 varient, the Canadair Mk6, was incapable of exceeding Mach1 inside 30,000ft, regardless of dive angle.

[Galvin]

My source says nothing about vertical dives being necessary to push the F-86 through the sound barrier but they may have been required for all I know. But that they were able to exceed Mach 1 from the very first airplane to the very last is a matter of record. It was "easy" for them to exceed to speed of sound in the sense that no special modifications to the basic airframe or special lightening measures as usually required on record versions of many aircraft were required in order to achieve it. It went supersonic right out of the box, just add testosterone and go.

The exact technique for getting up to speed was not explained, just that it was accomplished many times over in the course of the aircraft's service career.

The airplane was very clean if not fitted with pylons, ordnance or tanks and the prototype was able to accomplish the deed on a good 1000 lbs less thrust than the production versions were later to be provided.

Easy or not, the fact that it was capable of going supersonic from the very first prototype is a matter of record and thus it is likely that it was indeed the first aircraft to do so.

[Britbrat]

Galvin, I'm not questioning the F-86's obvious supersonic credentials -- just the timing.

[Wayne]

My father-in-law used to fly them....they used to stagger up as high as it would go 45,000+ and roll into a dive....sometimes they would break mach, and sometimes they would not.......

[RonMiller]

So, if Chuck Yeager was not the first to make mach 1, and the feat was in fact hush hushed, I have to think that many many other things have been quashed too. Anybody have any stories to tell?

[Britbrat]

I used to fly them myself -- that's why I don't believe the pre-X1 event. The late model Sabres could get well above 50,000 ft & usually didn't have any trouble exceeding Mach 1, but it just wouldn't work trying below ~ 30k ft