When jet-powered combat aircraft first started to enter service in the mid-1940s, the US Navy was an early and enthusiastic adopter of the new technology. But they very rapidly hit a quandary.
The initial jet aircraft had been straight wing planforms, similar to the propeller driven aircraft they replaced. But even before the end of the Second World War in 1945, engineers had recognized that that to get the best performance, swept wings were necessary.
The trouble was that these created problems with much higher landing speeds. This wasn’t such an issue for land air forces, they could build longer runways. But for carrier aircraft, which needed stable low speed characteristics as they smacked onto a tiny flight deck, it was a real problem.
If the Navy went with building designs that had straight wings, they made carrier operations much safer, but ran the risk of operating aircraft that would always be inferior to land-based opposition. If they built swept wings, they could produce much more effective combat aircraft, but at the risk of them being extremely dangerous to operate.
How could they combine the low-speed stability of the straight-wing with the high performance of the swept wing?
Naturally it was Grumman – the US Navy’s prime aircraft producer – that came up with a solution.
Variable geometry wings.
This sees the wings capable of pivoting – therefore providing a wide planform for low speeds and a swept wing for high. Nowadays, we are used to aircraft with this configuration, but it was a revolutionary idea at the time. No aircraft utilizing variable-geometry had actually flown at that point; the first – Bell’s X-5 – was in development.
Grumman was making a huge technical gamble. Unfortunately, their aircraft – the XF10F Jaguar – didn’t pay out.
Or at least, not initially.
The Jaguar originated as Grumman’s Model 83, essentially a cropped delta-wing version of the F9F Panther that was in service with the US Navy. The idea was that F10F would be an evolution of the F9F and use several components of that aircraft in its construction.
Grumman issued their proposal to the Navy in September 1947, intended for it to have the afore mentioned delta wing, combined with a T-tail. Powerplant would be a Pratt & Whitney J42 turbojet engine, an American version of the British Nene, and armament four 20mm cannon, as well as hardpoints for bombs and rockets.
Though they ordered the G-83 for prototyping, the US Navy’s Bureau of Aeronautics weren’t particularly keen on the existing concept. So, they started messing around with it.
First thing they wanted was to dump the engine, and instead the Jaguar would have the new Westinghouse J40 axial-flow turbojet engine then in development. They also wanted radar, specifically the APS-25 that would be built for the F10F.
All this screwing around with the very fundamentals of the aircraft meant it wasn’t until December 1950 that an actual specification for the XF10 was agreed upon.
The aircraft was to be a shoulder-wing monoplane of all-metal construction. The nose would house the radar, and armament would be four 20mm cannon along with a maximum bombload of four thousand pounds of bombs or rockets on two underwing hardpoints.
The tail was of unusual design as well. The horizontal stabilizer was free-floating with a small foreplane directly controlled by the pilot. This moved the stabilizer up or down, more like a miniature trim tab on an elevator.
Powerplant was intended to be the Westinghouse J40-WE-8 turbojet rated at 7,400 lbf dry and 10,900 lbf with afterburner. This was expected to give the production F10F-1 a top speed clean of 710mph
The final design of the Jaguar, as it was later to be designated, was therefore a much larger and heavier aircraft than had been initially projected with the G-83 concept – in fact about two-thirds heavier and a third longer. This led to Grumman’s suggestion to use a variable-geometry wing.
It also used very little from the F9F, with just a few parts of the cockpit structure in common.
And so, the F10F Jaguar was going to be a new aircraft that utilised an experimental engine and a revolutionary concept for flight modelling that hadn’t even been made to work properly by that point. Just getting some of these things to work at an experimental level would be – and indeed were at the time – full-fledged development programs.
But with Jaguar, the Navy wanted an actual service aircraft, not just a proof-of-concept.
Of course, we should also bear in mind the circumstances of the time. The Korean War had broken out in June 1950 and military spending shot up. So in August 1950, even before the specification had been settled, the US Navy ordered ten preproduction aircraft. This was followed shortly by orders for 123 F10F-1 fighters and eight F10F-1P reconnaissance aircraft.
With money basically no object, pre-orders on the books before a prototype had even flown and built exactly to the customers specifications, everything looked rosy for the Jaguar.
It would have to be catastrophically bad to not make the cut by that point, right?
Yep.
The prototype XF10F first flew on May 19, 1952 in the capable hands of test pilot Corwin “Corky” Meyer. But just getting to that point was a major achievement.
Meyer was a hugely experienced test pilot, having been a project pilot on many Grumman aircraft, performed assessments on the Japanese Mitsubishi A6M during the Second World War and been the first to fly the F9F prototype, Grumman’s first jet.
“…when I made my first run to “attempt” a liftoff, it was obvious to the audience that Grumman had come up with an airplane that would fly strangely, if at all. The airplane and I lurched up and down the runway as if one or the other, or both, were drunk.
“These attempts to fly went on for a week or so, causing much hilarity, but my real concern was that I couldn’t get the necessary feel or the required guts to fly it higher than 10 feet from terra firma.
“On May 19, 1952, I got the Jaguar up to 160 knots on the runway, at which speed the canard tail was found to have sufficient control for a first official flight. It was a disaster as far as accomplishing anything was concerned because just about every system refused to work.”
This set the pattern for the XF10.
Over the course of some thirty-two flights that Meyer made, the aircraft exhibited some nasty characteristics. At its best the aircraft was very sluggish, but at its worst it was bloody dangerous. The novel tailplane arrangement reacted poorly but could also set up violent oscillations in the aircraft. Stalling characteristics were described as vicious and considerable work went into altering the aircraft to remedy this.
Worse, the engine proved extremely poor. The J40 never achieved it’s expected output, plus the afterburning version that was intended for the production version didn’t pass reliability testing until 1952 and was thoroughly dismal.
Every test flight seemed to show up a new problem. For example, on the 23rd test flight, the canopy shattered completely, leaving only the frame.
Meyer needed to put the XF10 down in a hurry and set about making an emergency landing in the long lakebed at Edwards AFB that was used for just such a purpose. Then his chase plane called him up to tell him the face cover on his ejection seat was flapping behind him in the slip stream, indicating that it was now active and liable to fire off at any moment.
Meyer described how:
“I reached back, grabbed the rubber handle on the curtain and put it between my teeth, thinking, “What a grade-B movie this is!
“As the face curtain had fully extended, I knew the seat was armed and ready to fire, so after touching down on the lakebed and still rolling 100mph, I hurriedly unbuckled, scrambled out of the cockpit and straddled the front fuselage ahead of the windshield, facing aft.
“I had managed to get back onto the ground, and I had no taste for an ejection seat killing me by blowing me several hundred feet in the air. Several miles later, the Jaguar came to a standstill on the dry lake after completing a wide ground loop.
“We later found that debris from the canopy had pulled the firing pin 99 percent out of its detent.”
The continuous issues with the Jaguar and the J40 meant that both were doomed. In April 1953 the Navy cancelled the whole project and the production orders for the type.
The one flying prototype of the XF10F and a second one under construction were then used for barricade testing and as range targets, and so the XF10F passed into history.
No one seems to have had anything like a nice word to say about it except the only man to have flown the aircraft, “Corky” Meyer, and that in a rather barbed way.
“It was a fun airplane for me to fly because it had so much wrong with it.”
He did also state that:
‘An English test pilot made the following complete report about another airplane he had flown, and it fit my total assessment of the Jaguar perfectly: “The entrance to the cockpit of this airplane is most difficult. It should have been made impossible!”’
But despite all the issues there was one great success to spring from the Jaguar. It’s novel variable-geometry wing planform, which on the face of it seemed the most complex part of the aircraft’s development, worked extremely well.
On all the flights conducted, only once did the controls for the wing sweep fail, and they then returned to default open setting to allow safe landing as they were designed to in such a situation. In fact, the variable geometry system, despite its complexity, was the one great success on the XF10.
And this would go on to pay dividends on a later Grumman naval fighter, the F-14 Tomcat.
So, the legacy of the XF10F Jaguar isn’t all bad.
Links:
https://en.wikipedia.org/wiki/Grumman_XF10F_Jaguar
https://cmchant.com/a-swing-wing-pioneer-the-gruman-xf10f-jaguar/
https://www.defensemedianetwork.com/stories/the-grumman-xf10f-1-jaguar/
http://www.anft.net/f-14/grumman-xf10f1.htm
https://www.flightjournal.com/some-days-you-should-stay-in-bed-2/
