U.S. Navy Aircraft History

By Tommy H. Thomason

Monday, February 26, 2018

F-111A vs B - What Drove the Weight?

Another opportunity to set the internet record straight: what drove the F-111's empty weight? Some assume that it was the Navy's carrier-basing requirement. That's not only in question but some of the Air Force requirements penalized the F-111B's empty weight.

It is true that carrier-basing imposes a weight penalty. The FJ-2 Fury weighed approximately 1,000 lbs more than the F-86 on which it was based, resulting it being underpowered with the Sabre's engine. (That was solved by putting an engine with more thrust in the FJ-3.)
However, the major contributors to that penalty are wing folding, high sink-rate landing strength, and tail/catapult hook components and mounting structure. The variable-sweep wing feature required by the Air Force for long-range deployment and high-speed ingress sufficed for wing folding. The Air Force requirement to land on unprepared fields (most runways in Europe were assumed to be cratered in the first day of the war) meant it had a pretty strong landing gear with excellent sink-rate capability. At that time, Air Force airplanes were equipped with tail hooks for emergency landings albeit not to the same strength as a carrier airplane's. Therefore, the F-111A was penalized only by the relatively inconsequential tail hook and nose-tow-launch attach structure (the F-111B's nose landing gear itself was different).

It's not clear which service was responsible for the side-by-side seating arrangement. It is true that the Navy's two-seat jet night fighters, the F3D and the stillborn F6D had side-by-side seating, in part because shortness is a virtue on a carrier and their radar antennas were humongous. However, I've seen no documented evidence that the Navy required side-by-side seating, other than stipulating a maximum length, which the Grumman F-14 accommodated with tandem seating. On the other hand, the Air Force insisted on a heavy and complicated escape capsule that the Navy had no use for. It was best accommodated with side-by-side seating.

The Air Force also insisted on a bomb bay for nuclear stores and its unprepared field requirement (look up California bearing ratio at your leisure) dictated really big, low-pressure tires. Both of those features resulted in big compartments in the airframe that added empty (no pun intended) weight.

However, the biggest Air Force weight penalty was probably imposed by the Mach 1, low-level ingress on a nuclear strike. That results in the need to design for a very high "q" (dynamic pressure) and gust loading of the structure, neither of which were a requirement for a Navy missile-truck loitering on a Combat Air Patrol station at altitude and then dashing off toward an incoming raid. Moreover, given that the Navy's F-111B was not a true fighter, it probably could have been designed for a load factor of 4 rather than 6.5, further saving weight.

It should be noted that one reason for the F-14 being somewhat lighter than the F-111B was that it didn't have any of those Air Force features other than the variable-sweep wing and moreover, the weight of the big Phoenix missiles over and above that of Sparrows was considered an overload from a structural strength standpoint.

Friday, February 16, 2018

One More Time, The Grumman F12F

This is not the Grumman F12F:

It is the Grumman Design 118, proposed to the Navy in December 1955. The Navy rejected it because they didn't want a second development program of a fighter powered by two J79s (the McDonnell F4H was already under contract) but suggested that Grumman go back to the drawing board and propose a single-engine, Sparrow-missile armed fighter to compete with Vought's proposal for a Sparrow-armed "Super" F8U powered by the P&W J75. Grumman did on 4 May 1956.  The Navy rejected it as well in favor of what became the F8U-3 in a letter to Grumman from the Chief of the Bureau of Aeronautics, RADM James S. Russell, dated 16 July 1956, Subject: Grumman Aircraft Engineering Corporation Model 118A Airplane; proposal for: "The recent receipt of more up-to-date engine data does not alter the relative standings of your design with others already programmed in the fighter field. The Chief of the Bureau of Aeronautics had therefore determined that the introduction of another design using the same engines and comforming to the same general operating requirements cannot be justified or undertaken." Neither Grumman or the Navy ever referred to either of these two proposals as the F12F.

There was a Grumman F12F but the designation was assigned to a production variant of the F11F powered by GE's J79. Grumman had proposed its J79-powered Design 98J to the Navy in January 1955 and then its Design 98L, basically the J with increased wing area, in February. The latter appears to be the basis for the purchase order and contract in August 1955 that the Navy created for two F12F prototypes, which were to be assigned BuNos 143401 and 143402. The following artists concept appeared in the Design 98L report dated 15 February 1955.

This is the US Navy's F12F Characteristics Summary dated 15 August 1955. Although there is no drawing, the dimensions and performance data match the Grumman 98L's including the wing area of 350 square feet and the single J79 engine. (The Model 118 and 118A had a wing area of 595 square feet; the former was to be powered by two J79s and the latter, by one J75.)
It is not clear that the contract was ever issued. It probably wasn't. In any event, it was canceled or terminated in January 1956, probably due to the demonstrated performance of the Vought F8U-1 that first flew in March 1955 and the need to fund the development of a competitor to the F4H. However, the Navy had contracted with Grumman in August 1955 to put the J79 in the last two F11Fs in the first production lot in parallel with their plan to buy the F12F. These were designated F11F-1F and were not canceled, since they would provide the Navy with J79 flight experience desired prior to the beginning of the F4H flight test program.

One or more aviation historians have inadvertently conflated the two programs and incorrectly concluded that the Navy contracted with Grumman for its twin-J79-powered Model 118 and designated it F12F. Another enthusiast subsequently speculated that it was given the popular name Lion, which some have accepted as fact as well. It was not.

Saturday, February 10, 2018

The A-12 Avenger II Program - The Fat Lady Finally Sang

I'm embarrassed to say that I neglected to cap this story off when she did back on 24 January 2014. The settlement, according to a Reuters article, was:

"(T)he Navy will receive three EA-18G electronic attack aircraft from Boeing, and a $200 million credit from General Dynamics toward its work on a new DDG-1000 destroyer."

For the Aviation Week report (it may have still been a weekly back then), click here.

For my penultimate post, which has links to prior ones: http://thanlont.blogspot.com/2013/06/the-12-avenger-ii-program-end-is-near.html

Wednesday, January 3, 2018

Pre-war Downward-Vision Windows

One of the interesting features I noticed early on as I grew better acquainted with the history and development of U.S. Navy carrier-based airplanes was the presence of downward vision windows on most of the early monoplanes. My first guess was that they were incorporated to somewhat make up for the reduction in downward visibility resulting from the larger wing located more directly under the pilot. An example is the XF2F-1. As in most of the biplane fighters, the pilot sat just aft of the trailing edge of the lower wing.

The most significant benefit from restoring a view directly downward would be the ability to better judge drift from a crosswind, which would provide better accuracy for the dead reckoning necessary to find your way back to a carrier on an otherwise trackless ocean.

And that would appear to be the case for the downward vision windows in the Brewster F2A Buffalo and the Grumman F4F Wildcat.
Note that the F2A window is huge relative to the F4F's, indicative of a lack of specificity for the requirement. The F4F window was not intended to be used to determine whether the landing gear was down, as some have speculated. The pilot can't see the wheels through the window even when the shock struts are fully extended.
The windows are also of no use in landing. A pilot uses his peripheral vision to judge height above, and position over, the runway and the LSO's signals when landing on a carrier.

My original theory, even if correct, doesn't hold for the bombers since the pilot in the biplanes was generally located over the bottom wing. In any event, the earliest monoplane scout bombers like the BT-1 and SBA don't appear to have had downward-vision windows. The follow-on Brewster SB2A, Vought SB2U, and Douglas SBD Dauntless and its replacement, the Curtiss SB2C Helldiver, did. In this case, they were sometimes referred to as Bombing Approach Windows. Note that these were all dive bombers.

This is the Naval Aviation Museum's SB2A when it was conveniently hung from the ceiling. Note the channels on either side of the window for the struts of the bomb-displacement mechanism.

The SB2U's were located immediately aft of the cowl flaps.

The SBD's was located just aft of the post for the bomb-displacement mechanism and is hard to see even in this excellent Miles Lombard photo.
 The SB2C's is even more rarely remarked upon. It was ahead of the bomb bay and aft of the oil cooler flaps on the belly. It was covered by doors, which kept the window clean until needed.
 I have yet to see a picture with these doors open. The SB2C-3/4 pilots manual states that they were "removed from the SB2C-4 and replaced with an access panel". That was the end of the use of bombing approach windows.

The monoplane torpedo bombers beginning with the Douglas TBD Devastator had a downward vision window but in this case, it was for use by the bombardier although the pilot could see downward through it as well. The TBD was originally intended to function as a level bomber as well as a torpedo bomber. In fact, the Norden bomb sight made famous by the Army Air Force was initially a U.S. Navy project. The bombardier would crawl underneath the pilots seat from his seat in the center cockpit to use it.
 Two large doors kept the window clean until needed.

The Grumman TBF was originally designed for level bombing using the Norden bomb sight as well,

In the following picture, the window, located above the number "8636", is covered by a protective flap.

The Vought TBU's bombing window and sight were similarly located aft of the bomb bay as well.

The final variation of the downward-vision window was present in the Vought XF4U-1, Grumman XF5F-1, and Bell XFL-1. In this case it was again a bombing window, but for very specific armament, small antiaircraft bombs housed within compartments in the wings.

The requirement also mentioned another purpose for the window:

As it happened, the antiaircraft-bomb requirement was dropped for F4U production (also see http://thanlont.blogspot.com/2008/06/antiaircraft-bombs.html) but the window remained for a time.

Sunday, October 1, 2017

The First Supersonic U.S. Navy Fighter?

That claim is made for the F8U/F-8 Crusader in the subtitle of Bill Spidle's excellent book on its development (see yesterday's post). Some might quibble with that (many think it was the F4D Skyray if the definition is restricted to supersonic in level flight) so I undertook to determine which airplane had bragging rights from that standpoint.

After World War II, the Navy embarked on an ambitious program to develop high-performance swept-wing jet fighters, contracting for the Vought F7U-1 Cutlass, Douglas F4D Skyray, Grumman F10F Jaguar, and McDonnell F3H Demon. All were intended to have afterburning engines and be supersonic, at least in a dive. The F4D was expected to be supersonic in level flight.

There is no question in my mind that XF7U-1 BuNo 122474 was the first U.S. Navy fighter to break the sound barrier, albeit in a dive and then only to Mach 1.006, on 21 June 1950. And that was with the aid of afterburning.

It was only capable of about Mach 0.9 in level flight. The thrust required as you approach Mach 1, the speed of sound (which varies with air temperature) is significant as depicted, approximately, in this illustration.
Note the dramatic steepening of the curve at about Mach 0.9.

None of the other fighters of its generation (or the F7U-3 for that matter) were capable of staying supersonic in level flight either. The XF10F was never dived faster than Mach 0.975 (for one thing, Grumman was never provided an afterburner for its J40 engine) in a single high-speed test flight on 11 October 1952, five months after its first flight. The sleek XF3H Demon, which first flew in August 1951, was probably the fastest, having been dived to Mach 1.3, but as far as I know, it never broke the sound barrier in level flight and the heavier production Demons were not as fast.

What of the F4D? Douglas projected its top speed would be Mach 1.2 in level flight. Its first flight on 21 January 1951 was with an interim J35 engine. After the more powerful J40 finally became available (without an afterburner), an XF4D was dived through the sound barrier in mid 1952. In October, finally equipped with an afterburner, it set an official absolute speed record on a three-km low-altitude, sea-level course of 753.4 mph. That wasn't, however, supersonic. The speed of sound at 15 degrees C and sea level is 761.1 mph but the successful attempt was made, deliberately so, when the temperature had reached almost 37 degrees C (even though it decreases engine thrust, a higher temperature is your friend when you don't have quite enough thrust to go supersonic in level flight) because that raises the speed at which the transonic drag increase begins. The speed of sound was therefore about 790 mph on the course, which means that the XF4D's speed was about Mach 0.95.

Although Douglas engineers and test pilots strove mightily to reduce the F4D's transonic drag and achieve supersonic speed in level flight, they were unable to do so, as reported by the Navy following its formal acceptance tests in late 1957.

If you restrict claimants to supersonic speed in level flight, there is one other contender, the Grumman F11F Tiger. It was probably the first fighter to be area-ruled by design. Grumman expected it to reach a level flight speed of Mach 1.21. Grumman received "go-ahead" for the program a month before Vought was notified that it had won the OS-130 competition. It first flew, as the F9F-9, on 30 July 1954. However, Grumman didn't receive an afterburner for it until late 1954 or early 1955 and the first attempt to fly supersonically with it on 25 January 1955 was terminated at Mach 1.03 when it failed catastrophically. Wright wasn't able to provide another flight-worthy one for more than a year. In May 1956, the F11F would finally just break the sound barrier in level flight; according to its Standard Aircraft Characteristics Chart, its top speed was Mach 1.1 at 35,000 feet. During BIS evaluation, it failed to meet guarantees but was definitely, if barely, supersonic:

Meanwhile, Vought had flown its F8U for the first time on 25 March 1955, breaking the sound barrier in the process, possibly but not necessarily in level flight.

Because of ongoing modifications required to make the F11F suitable for operational use, the F8U was delivered to VX-3, the cognizant Navy Air Development squadron, in December 1956, whereas it didn't receive its first F11F until February 1957. However, deliveries to operational squadrons of both airplanes were made in March 1957 and VX-3 took both aboard for at-sea evaluation in April. In the end, although probably not predicated on the fighters' respective readiness, VF-32 deployed with its F8Us aboard Saratoga on 1 February 1958 while VA-156 with F11Fs didn't go out aboard Shangri-La until 8 March 1958.

So Grumman received a contract for the supersonic F11F a month earlier, flew for the first time several months earlier, went supersonic two months earlier, and then faltered on the back stretch, finally deploying in what amounts to a dead heat. It should also be noted that the F11F was just barely supersonic in level flight, while the F8U was really supersonic. Although when the excellent J79 was substituted for the so-so J65, the F11F could arguably match the F8U in speed and altitude capability...

After all that, I think the edge goes to the Crusader over the Tiger for the first supersonic U.S. Navy fighter but it depends on your definition of what constitutes "first" and it won't be by much.

Saturday, September 30, 2017

Vought F-8 Crusader by William D. Spidle

If you're considering buying this book—and you really should if you have any interest in carrier-based airplanes—note the subtitle. It covers the predesign, proposals, engineering design, test (and tragedy), and marketing (think record-setting) of the Crusader and its derivatives from Vought's vision of a true supersonic carrier-based fighter through their retirement. Look elsewhere if you prefer stories beginning "There I was, upside down, in cloud, on fire, nothing on the clock except the maker's name, when suddenly...". There are several available of that genre on the F-8, whereas there are none about it that go into this level of illustrated detail.

Bill Spidle is uniquely qualified to be the author. He had unfettered access to the Vought archives that were maintained by Vought-retiree volunteers and stuffed with documents, pictures, reports, etc. contributed by Vought employees over time. Rare among company archives (some now jealously guarded and almost unavailable to researchers by the company that had absorbed them), Vought's were accessible. In exchange, he helped review and catalogue the material for several years. As a result, his book incorporates pictures, illustrations, and information not only not previously published but which I had not seen before.

Another point to consider is that it is published by Specialty Press, which is once again adding to its sales catalogue of aviation books. As a result, it is a large format (10 inches square) tome with many color and high-resolution photos printed on heavy, glossy paper, a joy to behold and peruse.

One note on the subtitle: The Navy's First Supersonic Jet Fighter. The first ones to reach the fleet were the swept-wing placeholders for those with afterburners that the U.S. Navy had ordered after World War II, the Cutlass, Skyray, Demon, and Jaguar. Like them, however, the F9F Cougar and FJ-2/3 Fury could only break the sound barrier in a dive. And that includes the F4D Skyray, often cited as the first Navy fighter to be supersonic in level flight. It was stubbornly subsonic except in a dive despite Douglas' best efforts to make it otherwise (more on that in another post). Some might argue that Grumman's F11F Tiger was the Navy's first supersonic fighter in terms of level-flight speed since it was on contract and flew before the F8U Crusader did. However, its initial flight test was without an afterburner, whereas Vought test pilot John Konrad took the F8U supersonic on its very first flight. Moreover, F8Us were delivered to Navy development squadron VX-3 in December 1956 whereas the first F11F did not arrive there until February 1957 after a somewhat protracted development required to make it satisfactory for deployment.

Saturday, August 26, 2017

Brewster F2A Buffalo

I have a soft spot for unappreciated or much maligned aircraft as you could tell from the subjects of most of my monographs, i.e. soft-cover books (see http://tommythomason.com/). I might have written one about the F2A Buffalo except that it was built in some numbers and saw service use, which requires a lot more research and insuring that the expected "war stories" are accurate and representative.

Fortunately, Captain Dann is more ambitious and industrious than I and Steve Ginter continues to be open to publishing monographs on lesser known aircraft. The result is an excellent history of the Buffalo, both the airplane itself and its service life in not only the U.S. Navy but other countries.

As importantly, they had the full support of Jim Maas, who is the go-to guy for Buffalo pictures, drawings, useage, etc.

The result is the most in-depth and complete book on the F2A that we are likely to ever have. The various types are described in detail with copious pictures and illustrations, including development and proposed modifications/improvements. Their usage is summarized by country and squadron and includes first-person commentary. Regardless of the extent of your knowledge of the type, I can all but guarantee that there will be pictures that you have not seen before and information that you did not know. (I was unaware of the one-off "XF2A-4", for example.)

As is customary in Ginter publications on specific types (see http://www.ginterbooks.com/), it concludes with a summary of model kits available. Note that you can buy them directly from him, which will help keep these histories of esoteric subjects coming.