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North American XP-86


Sabrejet

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John R recently asked about details of the XP-86 so I thought I would post what I have. It's a convoluted story and it may take some time, but to cover the XP-86 I need to start with the closely-related FJ-1 Fury. Yes, the FJ-1 was a tubby, straight-winged object, but for a while so was the first version of the Sabre.

 

Though a bit messy, this drawing is the earliest one I've found for the XFJ-1 prototype Fury (North American Aviation (NAA) Model NA-134). It's a 13 October 1944 NAA drawing for a proposed "JP Shipboard Fighter" (JP being "jet powered").

 

1

 

I've highlighted a few key items and appended a few dimensions on this version. Notable are two items which did not make it on to the FJ-1 Fury: the wing-mounted dive brakes (also planned for the XP-86); and the folding wings (line/dotted line shows angled wing fold top/bottom joint).

 

1a

 

Frontal view shows that a ventral tank was planned (again, not taken up in production). Also note that there is no dihedral on the tailplanes:

 

1c

 

Side view from same drawing set of October 1944:

 

1aa

 

Assigned the NAA Model number NA-134, this NAA artist's impression dates from 4 October 1944 and reflects the drawings above.

 

2

 

I won't go into the FJ-1 in any detail, but for comparison the following 3-view shows that the production FJ-1 Fury was generally smaller than the initial October 1944 proposal:

 

1d

 

So to start with the XP-86. In 1944 the USAAF had issued a design request for a medium-range day fighter, and NAA submitted a version of its NA-134 (FJ-1) on 22 November 1944, and this design was given the NAA model number NA-140. The NA-140 was very similar to the NA-134, but this early model shows that already the NA-140 had gained a 'lip' to its engine intake and retained the less tubby lines of the "Shipboard Fighter" drawings. NA-140 would be designated XP-86 by the USAAF.

 

1b

 

But towards the end of WW2, swept-wing data started coming in from NACA and also from captured German files, which led NAA to look at a redesign of the NA-140 with swept wings. Different aspect ratios ("AR" on the wind tunnel model drawing below) were looked at for the mainplanes. This one is from 23 April 1946, when a straight fin and tailplane was still part of the design:

 

1e

 

And finally, by 15 October 1946 a fairly definitive version had been arrived at:

 

1f

 

More in the next instalment: maybe some good ideas for "what ifs" here?

Edited by Sabrejet
Updated to rectify Ph*tobucket self-destruct issues
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23 minutes ago, Tailspin Turtle said:

Thanks very much for those illustrations and comments. Note that the FJ-1 prototype did have the wing-mounted speed brakes but the production Furies did not.

 

Correct: the XFJ-1 did have those brakes: one of the NAA guys told me that they were hastily deactivated because when extended the braking force, "...nearly made the pilot's eyes pop out!".

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One item which did not make it into production was the dive brake arrangement that was actually installed on the three XP-86s (s/n 45-59597 thru 599). Best described as 'folding' in the way they operated, each panel (two side and one ventral) were actuated by two hydraulic rams (ventral) or three (side). This early NAA rendition gives an idea of their location and operation:

 

1g

 

This view of a NACA wind tunnel model shows a similar early iteration of the brake arrangement:

 

4

 

As stated, these brakes were actually installed on the XP-86s but by the time of roll-out further wind tunnel tests had shown that they would not work. NAA aerodynamicist 'Mac' Blair revealed that, "It became obvious that the original 86 brake design was unsatisfactory: there was far too much drag area, the pitch trim changes would be terrible, and the [rear-hinged] brakes would fail open with the loss of hydraulics.” 

 

And so, until a better solution could be designed, tested and put into production, the XP-86 speed brakes were inactivated and never used: since testing at Muroc (Edwards AFB) used vast expanses of available runway, speed brakes were less important during the testing phase.

 

Because of this it is difficult to find much data on the actual speed brake design of these aircraft, but the following is the best I have found that shows the 'as-installed' version. Note that on this drawing, the speed brake rams are mounted differently. I trust this version below, since it was part of a flight test report showing pressure readings and therefore most likely to be representative of the actual XP-86. The ventral rams for the bottom door were mounted on Frame 244.75; the forward ram of the side speed brake on Frame 286.5; and the aft rams (top one mostly obscured in the drawing) of the side doors just forward of Frame 352.47.

 

3

 

First known photos of the completed #1 XP-86 date from 14 August 1947, taken at NAA Inglewood and showing the aircraft ready for inspection by the Air Force ‘689 Board’:

 

d (1)

 

Below the same view annotated to show key points (I will refer to other items in a later post): 1 - 'long' canopy (see F-86A Wing thread - this is the same-length canopy perspex fitted to F-86A-1 aircraft); 2 - small intake, covered over prior to/just after first flight; 3 - Brake covers: though these were installed on other F-86 types, they are not often seen (see photo below); 4 - No fuel vent mast installed at this point; 5 - Pointed tail fairing, with no tail lights; 6 - Original 'production' airspeed/pitot probe location (no intake-mounted probe at this point); 7 - Tail lights: red at top, white at bottom; and 8 - though not visible, the #1 XP-86 had instrumentation booms on each wingtip: airspeed on stbd/right and yaw/pitch on port/left. Whilst the #1 XP-86 was at Inglewood, the booms were installed but not the actual probe heads (i.e. the bit at the end of each probe). Both booms were removed when the XP-86 was broken down for road transport to Muroc for flight testing. 

 

d (2)

 

This shot gives a better idea of what the brake cover looked like: I don't think it's ever been represented in a Sabre kit - ?

 

brake_zpsbpygzv6x

 

I apologise for the next photo, which I do not have a proper copy of: it shows the #1 XP-86 outside at Inglewood and shows the markings and general appearance of the XP-86 just before it was trucked to Muroc. There are a number of publications which show an unmarked NMF Sabre and captioned as showing the #1 XP-86 but actually depicting an early F-86A-1.

 

j (8)

 

The #1 XP-86 began taxi trials from mid-August through early September 1947 at Inglewood's Mines Field. PU-597 was then disassembled and trucked to the South Base area of Muroc Field, where it was off-loaded on 11 September.

 

Next I'll cover the configuration changes made at Muroc.
 

 

Edited by Sabrejet
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Muroc, late September 1947: these were all taken around about 29 September when George Welch did Taxi Test #1 and Taxi Test #2. 

 

Key points: 1 - NACA Swivel Airspeed Probe (see diagram below); 2 - Single-piece nose door; 3 - Aileron trim tab (LH/port side only); 4 - Pitch/yaw probe; 5 - No fuel vent mast; 6 - Difficult to see (but more visible in other images) an NAA logo was placed in this position either side of the cockpit area (see image below).

 

j (14)

 

Tail view taken at same time as above: note that the speed brakes are taped-over and the buzz number etc painted over the tape. Also I have highlighted the aileron trim tab and circled the small intake which was on the LH side only. Note also other things, such as lack of antenna bowl beneath the canopy and the pointed tail fairing.

 

j (15)

 

Another Muroc photo taken around the end of September to 1 October period: 1 - NAA logo and 2 - Two temperature 'bombs' under nose section.

 

j (1)

 

NAA Logo:

 

d (3)

 

NACA swivel airspeed head (RH/port-wingtip boom):

 

d (4)

 

Fuselage, wing and tailplane stations, XP-86:

 

d (5)d (7)d (6)

 

 

 

A few diagrams of the unique-to-XP-86 nose landing gear. The cylindrical steering actuator was different to those fitted to F-86A/E/F etc:

 

img030a_zpsgbkahnbpimg034a_zps5rza2iupimg035a_zpsdui52djf

 

 

 

 

 

 

 

Edited by Sabrejet
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Final bit for today. The XP-86 instrument panel was a different shape and configuration to other F-86s. These diagrams show what was where and the photo (of the #3 XP-86, with a simple gunsight/camera which was not fitted to the #1 XP-86), though not great, does at least show how the main instrument panel differed in shape at its top edge.

 

001 (4)

 

001 (3)

 

001 (1)

 

001 (2)

 

001 (5)

 

More soon: I hope this is of help.

Edited by Sabrejet
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5 hours ago, Sabrejet said:

 

Correct: the XFJ-1 did have those brakes: one of the NAA guys told me that they were hastily deactivated because when extended the braking force, "...nearly made the pilot's eyes pop out!".

I had heard that one time too many, one brake extended and the other didn't.

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1 October 1947 onwards:

 

Not a brilliant image (taken from a film), but showing the XP-86 first flight, where the nose landing gear failed to retract correctly on take-off: Welch spent the rest of the flight cycling the gear and trying to coax it down.

 

06 01Oct47_zpshscxpbwe

 

I'm fairly certain that this shot shows the end of the first flight: it's certainly early in the programme:

 

07 1a_zpsxv10jmrt

 

Images taken around the time of the first flight: note that the #1 XP-86 has now gained a fuel vent mast (though not in the standard location).

 

07 2_zpst3hbe6sb

 

Comparison of XP-86 fuel vent position and the standardised F-86A location. Note also that the trestle lines (black lines under the aft fuselage) are different XP-86 vs. F-86A:

 

06a_zpsgwblllit

 

Flight 2 on 9 October 1947 was made with the gear locked down due to damage incurred on 1 October maiden flight. Note that the aft speed brakes have been re-taped (black horizontal lines) compared to previous view. Black tape was only present on RH side.

 

09 09Oct47 3_zpsjzclcbqs

 

09 1_zpsipz1osm5

 

 

 

 

Edited by Sabrejet
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Photos taken mid-October to early November 1947: Note how the wing slats act as independent sections (later joined together to act as one panel per wing and standardised as such on F-86A). Also circled small vent (refer to previous photos) has been filled. Also a good view (top) showing temperature 'bombs' and taped-up ventral brake panel.

 

11 8_zpsbzsd61wa

 

11 6_zpsax5dtam7

 

 

 

 

Edited by Sabrejet
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13 November sortie with NAA badge just visible below the fwd windshield (it's possible that the above two images were taken at this time too):

 

11 13Nov471_zpsscpag4mb

 

3 December 1947 sortie:

 

12 03Dec47 3_zpscearrjev

 

Some time between 3 and 8 December 1947, a red turbine warning stripe was applied. This image dates from that 6-day window and also shows a long pitot tube mounted on the tail fin: on Flight 26 in late November, a chord-length pitot boom had been trialled but this version is even longer.

 

13_zpshyftufov

 

Edited by Sabrejet
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Circa 8 December, a second mid-fuselage vent was added (circled). 

 

14 08Dec47_zps6prw6uci

 

Shortly after 8 December 1947, a pitot probe was mounted on the LH/port wingtip in place of the pitch/yaw head which had previously been installed there (compare with photo above). The pitot boom was red in colour and the boom of the stbd/RH NACA swivel head was also painted red around this time.

 

16 3_zpsdsnwls4h

 

16 4_zpsx5rz36oo

 

This underside view (similar to the above) from around mid-December 1947 shows the newly-installed pitot boom on the LH wingtip and also how dirty the underside had become in the month or so since the previous similar shot.

 

16 5_zpswfmdebeo

 

Undated, but likely taken towards the end of 1947 or early 1948, the #1 XP-86 with short-lived long range fuel tanks. Note also that the upper mid-fuselage intake has also been blanked off:

 

17_zpskvvwilxl

 

Edited by Sabrejet
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Following flight number 77 in January 1948, the XP-86 was grounded for a 25-hour engine inspection. The opportunity was taken at this time to incorporate several modifications, and among these was the fitting of a new rear fuselage with the production-standard standard speed brakes. However it would seem that this new aft fuselage section was a combination of XP-86 and F-86A, with the conventional speed brakes, but retaining the fin tip-mounted tail lights and pointed tail cone of the XP-86.

 

The following photos post-date the fitting of the "XP-86.5" tail and must date from June 1948 or later, when the 'PU-' (pursuit) buzz number prefix changed to 'FU-' (fighter). Also visible on the Tech Data Block (below the LH windshield) in the original photo can be made out the script, "U.S.AIR FORCE    XF-86" - again, the XP-86 experimental pursuit became an XF-86 fighter on 1 June 1948.

 

Also of note: circa June 1948 the #1 XF-86 was painted in an off-white ‘Superfine’ paint finish overall. According to an NAA Tech Rep, this surface finish had been planned for all production F-86s, but tests on ‘597 showed that it did not wear well in a maintenance environment and was easily degraded by hydraulic fluid.

 

Note also the revised mid-fuselage intake, which is now a shaped vent: this design was incorporated into the other XF-86s around this time. The yaw/pitch head has also been reinstated on the port/LH wingtip.

 

18 circa Jun48 4a_zpsosmbvutv

 

18 circa Jun48 1_zps4xddvvm2

 

 

 

Edited by Sabrejet
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The #1 XF-86 was accepted by the USAF on 3 December 1948 and assigned to Wright-Patterson's 2750th Air Base Group on 12 December in a test role. Prior to handover to the USAF, it (as with the other two XF-86s) had the Allison J35 engine replaced with a GE J47. At the same time, a full F-86A-standard rear fuselage was installed. The #1 also gained the AN/ARN-6 radio compass loop antenna dome beneath its aft canopy section for the first time. Photos of the aircraft are rare during this period, but the following show the #1 XF-86 during its time assigned to USAF test. 

 

19 1_zpse3abspjn

 

19 2_zpsxix0zbpn

 

 

EDIT: while I remember, the #1 XF-86 was the only Sabre to be fitted with a fire extinguisher system (all other Sabres had warning lights which told you when to eject): this is a schematic of '597's unique system:

 

 

img039_zps5hhivsbx

 

 

Edited by Sabrejet
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Final phase of the #1 XF-86's existence: from Wright-Patterson it was transferred to 2759th Experimental Wing at Edwards AFB on 2 April 1951; initially as an Air Materiel Command asset, but with a change to Air Research & Development Command on 2 April 1951 its assignment at Edwards was with 6510th Air Base Wing.

 

Finally, on 5 May 1952 the aircraft is shown as being reassigned to 4901st Support Wing at Kirtland AFB, New Mexico and tested to destruction there on 2 September, with a strike-off date of 3 October. However the truth is far more dramatic.

 

Sometime prior to April 1952, s/n 45-59597 was moved to Yucca Flat at the Nevada Proving Ground (and possibly flown into the test site’s airstrip on Yucca Lake) for use as a static test airframe during nuclear weapon tests. It was later moved to the site at Frenchman Flat, approximately 20 miles SSW of Yucca Flat for further testing.

 

There it would be destroyed during Operation Upshot-Knothole, the ninth series of atmospheric nuclear weapons tests conducted by the Atomic Energy Commission (AEC) at the Nevada Proving Ground and running from March to June 1953. 

 

The XF-86 was still largely intact until it was exposed to the detonation of Shot Grable on 25 May 1953. Grable was an atomic artillery projectile with a yield of 14.9 kilotons and fired from a 280mm cannon toward Frenchman Flat. 

 

For this detonation, the #1 XF-86 was placed nose-on to the blast and 1850 feet from ground zero. To quote the contemporary report on the effects of Shot Grable, “The [X]F-86 aircraft was annihilated. The only portion of the aircraft left relatively intact relatively intact was the engine, which was found some 500 ft further from ground zero than its original position.” Thus ended the existence of this pivotal machine, in the Nevada desert on 25 May 1953. The following blurry photos date from that time: black areas in the final (circa May 1953) image are scorched fibreglass components from previous nuclear tests.

 

20 2_zpsnqfzoxrz

 

20 1_zpspmjkgb6o

 

21 2_zpsk6gdvjfs

 

 

 

 

 

Edited by Sabrejet
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  • 2 months later...

Would it be possible to update this post with photos from another photo host sight? Photo Bucket is now charging to allow 3rd party image posts so the photos have been blocked. Sounds like there are a lot of interesting photos that are now not visible. Love to be able to see them.

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