U.S. Navy Aircraft History

By Tommy H. Thomason

Thursday, May 21, 2015

American Military Training Aircraft

This latest book from E.R. Johnson, published by McFarland, is a comprehensive encyclopedia for aviation enthusiasts of U.S. military trainers, including gliders and helicopters. While perusing its 480 pages, you’re pretty much assured of coming across more than one aircraft of which you were previously unaware. In the event that you hear or read about a trainer with which you are unfamiliar, you’re almost certain to find a summary description of its career—however short or even non-existent—along with a data table, at least one photograph, and a multi-view drawing (by Lloyd S. Jones) of the type in this book

As a handy reference, it is a suitable companion to Johnson’s American Military Transport Aircraft Since 1925, reviewed by me here: http://thanlont.blogspot.com/2013/04/american-military-transport-aircraft.html, and United States Naval Aviation 1919-1941, http://thanlont.blogspot.com/2011/06/united-states-naval-aviation-1919-1941.html

Like Military Transport Aircraft and United States Naval Aviation, it is soft cover and there are no color pictures. It does include an appendix describing the U.S. military trainer designation systems, which changed over time. There is also a very useful glossary and a comprehensive index, which will be invaluable in a search for a particular type covered by the book.

Try as we authors might, it’s virtually impossible to have a book published without error or typo, particularly one of this extraordinary breadth. For example, I only recently realized that the T (for trainer) designation of the Grumman TF (C-1A) Trader was based on its original justification in large part as a trainer rather than being “anomalous” as Johnson reports. See http://thanlont.blogspot.com/2012/06/designation-story-redux.html. Jones’ drawing labeled as the T-37A has tip tanks that were only present on the T-37C (procured by foreign governments but not the USAF) and the A-37A and B Dragonflies, which were not trainers, per se. Hopefully these slips are few and far between. I believe that they do not detract from the overall usefulness of the book. (I was particularly pleased to note that Johnson avoided a common error by not ascribing dual controls to the Douglas A3D-2T (TA-3B).)

McFarland's website to order books is www.mcfarlandpub.com; the order line is 800-253-2187. American Military Trainers is also available from Amazon both in hardcopy and as an ebook (see www.mcfarlandpub.com/customers/ebooks for other providers).

Tuesday, May 19, 2015

Fitting In V

All U.S. Navy carrier-based airplanes being developed at the beginning of World War II had folding wings and there was only one exception thereafter, the A4D Skyhawk; its span was specifically limited to the maximum dimension generally acceptable for a folded airplane. See http://thanlont.blogspot.com/2012/12/fitting-in-iv.html

There were, however, airplanes with specific limitations or issues that meant they weren't always folded at all times on deck. For example, the McDonnell F2H-2 (and reportedly the -3 and -4) Banshee's wings could not be folded or unfolded with full tip tanks. As a result, they had to be spotted with the wings unfolded for fueling before flight if the tip tanks were to be filled.

In order to minimize weight, the North American AJ Savage's wings and vertical fin could only be folded after the deck crew bolted a hinge to the fold joints along with a folding device, hydraulic for the wings and manual for the vertical fin. As a result, they weren't often folded.
U.S. Navy via Greg Bishop

Although the Douglas AD Skyraider's wings could be loaded with bombs and rockets when folded, it was sometimes more convenient to arm one with the wings spread.

Wednesday, May 6, 2015

Carrier Landings: Visibility Over the Nose

One of the differences between a land-based airplane and a carrier-based one is the need for over-the-nose visibility down and to the left. In the beginning, it was to be able to see the Landing Signal Officer (LSO) on the approach until the cut or wave off.
Here, the LSO is either signaling high or wave off (for the signals, see http://thanlont.blogspot.com/2012/11/waving-them-aboard-lso.html

There was a more relaxed approach to the requirement when airplanes were pulled by propellers. Douglas stuck an antenna mast squarely in the pilot's line of sight to the LSO on the SBD.

When Vought moved the F4U Corsair's cockpit back in the production redesign, the loss of visibility was significant.
Pilots, however, coped by approaching the carrier in a turn, only straightening out when the LSO would stay in view.

Jets approached somewhat faster than propeller-driven fighters so a visibility requirement was instituted. It failed to take into account the extreme nose-high attitude required at slow speed by the F7U Cutlass, since it could not have flaps.
The lack of visibility was recognized early on.

Nevertheless, the Navy proceeded with at-sea trials, which were accomplished by using a side slip on a straight approach.
(The LSO is signaling high.)

As a result of the experience, a redesign of the F7U's cockpit and forward fuselage was required.

The first version was also deemed to be unacceptable, requiring another redesign of the cockpit, canopy, and radome before at-sea trials.
Douglas almost made the same mistake with its F4D but recognized it before beginning detail design. A quick and dirty modification of the mockup was evaluated.

When the Navy was forced by the delays in its fighter development programs to adapt the Air Force's F-86 to the carrier-based FJ-2 Fury, BuAer stipulated "that the angle of the approach sight line with the airplane in the static attitude not be less than 17 degrees below the horizontal with the seat in the full-up position." This required a redesign of the windscreen.
This change proved to be inadequate during the at-sea trials.
As a result, the windscreen was redesigned for production.
 In addition, the interface between the sliding canopy and the fuselage was changed. The XFJ-2 used the same sliding canopy as the F-86.
For production, the first two feet of the canopy movement was angled upward, providing for a higher seat position that did not require the pilot to duck his head when the canopy opened and closed.

This change further improved over-the-nose visibility and was continued forward to the FJ-3.

Perhaps the ultimate in over-the-nose visibility in a carrier-based fighter was achieved by McDonnell with its F3H Demon.

Sunday, March 29, 2015

New A3D/A-3 Skywarrior Monograph

If you have any interest in Whales, naval aviation, or the Vietnam War, you should buy this book. While the title seems to limit it to the Vietnam War, Rick also summarizes the airplane's origin story and post-Vietnam career. For more of what it includes and some five-star reviews by people who know what they're talking about, look it up on Amazon.

Wednesday, March 25, 2015

Happy Birthday, Vought F8U Crusader

On 25 March 1955, the Vought F8U-1 flew for the first time. I almost missed joining the celebration. For an excellent and well-illustrated example, see here: http://voughtworks.blogspot.com/2015/03/xf8u-1-crusader-at-60-part-v.html

The milestone was even more significant because it included breaking the sound barrier. First flights are usually planned to minimize risk, with the primary objective being photos, not envelope expansion. And in this case, supersonic flight was not only not a sure thing but the ability to do so, somewhat of a concern.

Richard Whitcomb of NACA experimented in early 1952 with reducing transonic drag by what he described as the area rule. The concept was that an airplane's total cross-section (area), including the wings and empennage, needed to smoothly increase and then decrease along its length. Because even a swept wing resulted in a fairly abrupt increase in cross section, that meant that the fuselage cross section had to decrease to compensate. He published a confidential paper on his theory and wind tunnel test results in September 1952.

Grumman engineers had already postulated the same theory and applied it to a fighter design study in late 1951. Note the distinctive fuselage "Coke-bottle" shape.*

The unsolicited proposal included the following illustration, clearly a representation of the area rule:

Convair was in the process of designing a new delta-wing fighter, the F-102, for the Air Force in 1952. Their wind tunnel testing indicated a significant drag problem at transonic speed that proved to be correct in flight test in 1954. As a result, they had to delay flight test and production in order to reshape the fuselage in accordance with area ruling to reduce drag.
 The delta wing created a large peak in the overall cross section near the wing's trailing edge that had to be offset by indenting the fuselage and adding bulges aft of the wing to more smoothly taper down the cross section.

Vought won the 1952 competition for a Navy day fighter with an innovative design that included a variable-incidence wing. It did not take into account area ruling, which at that point was still a theory backed up by wind tunnel test of notional models.

The Navy awarded Vought a contract for the F8U in mid-1953 and encouraged the company to consider incorporating the area rule. After careful consideration and evaluation of its wind-tunnel test predictions, Vought was not inclined to do so. The necessary shaping of the fuselage cross-section was onerous from a weight and manufacturing cost standpoint; it also affected the internal volume needed for fuel. NACA tentatively agreed that the high fineness ratio of the F8U and its relatively thin wings probably sufficed from an area-rule standpoint.

In late 1953 and early 1954, however, the results of NACA wind-tunnel and rocket-propelled F8U model testing at transonic and supersonic speeds indicated that drag was likely to be higher than Vought had projected.
 From Joe Chambers' excellent monograph: http://www.nasa.gov/pdf/483000main_ModelingFlight.pdf

Vought began to take the problem seriously and define changes to take area rule into account, but like Convair, successfully lobbied to not make major changes in the prototype in order to fly on schedule. According to a NACA memo, these would be evaluated in wind-tunnel test with the intent  of incorporating them in production at ship #75.

Before first flight Vought was able to sharpen the forward fuselage by extending the nose cone about three inches (it had become shorter and more bulbous than shown on the mockup), reducing the size of the canopy, and incorporating a sharper inlet lip.
(It's not clear when the cannon were relocated aft; that may have occurred before the area rule improvements, possibly for weight and balance.)

The aft fuselage was reshaped and extended as well to smooth the decrease in cross section.
As it turned out, the NACA test results were pessimistic and these initial changes proved to be all that were necessary, along with the fact that the combination of long slender forward fuselage of the F8U, lack of bubble canopy, and the close coupling of the empennage to the wing resulted in a shape not far from the ideal one. The additional changes were cancelled.

Vought management and engineering must have been greatly relieved, particularly after Convair's struggle with the F-102's excessive drag. Ironically, the competition, Grumman's beautifully area-ruled F11F Tiger that resulted from its 1951 design study, lacked both performance (it had a less powerful engine) and also enough internal fuel, unlike the F8U. (Also see http://thanlont.blogspot.com/2009/02/area-rule.html)

Vought learned its lesson about area rule, however. When incorporating the camera installation in the photo-reconnaissance variant, F8U-1P, it was taken into account. See http://tailspintopics.blogspot.com/2013/12/photo-gator.html

* A "Coke bottle" shape is aptly descriptive to those of us of a certain age:

Sunday, February 22, 2015

Swept-Wing Tip Skid

Bob Sikkel called my attention to a detail on the McDonnell F3H-2 Demon that I hadn't noticed before, a post-mounted blivet out on the underside of the wingtip. I found excellent pictures of it in Don Hinton's walk-around photos of the F3H-2 at the National Museum of Naval Aviation in Pensacola.

Note that the "saucer" of the skid itself is clearly intended to be readily replaceable.

It's a definite oddity, since I don't remember anything like it on other Navy swept-wing jets. I was familiar with the XF3H-1 originally having a much longer version of it.

However, that skid disappeared from the XF3Hs when the wing was changed to move the ailerons inboard.

Nevertheless, a very short tip skid turns out to have been incorporated on the ill-fated production F3H-1.

And it is present on the F3H-2 wingtip in almost every picture of it with sufficient resolution to discern it. It is identified in a F3H maintenance-manual illustration as the "wing tip skid". (Thanks to a Royal, a volunteer at the Emil Buehler Library at the National Naval Aviation Museum, for finding that for me.)

So what was that all about? The only other evidence of a similar device is on a circa 1946 Douglas predesign three-view of its D571-1, the predecessor to the F4D Skyray.
I haven't seen any evidence of one on either the F4D mockup or XF4D prototypes.

The Navy was nervous about the approach-speed handling qualities of a swept-wing carrier-based airplane so they contracted with Bell for a swept-wing conversion of its P-63, designated the L-39, in 1946. (Also see http://thanlont.blogspot.com/2011/04/bell-l-39-wing-sweep-evaluation.html)
There's no evidence of tip skids on it or any mention in the flight test evaluation of the need for them.

If there was a concern at the Bureau of Aeronautics about swept-wing tip contact with the deck/runway, it didn't reach Vought or was ignored in 1945 when it was proposing what became the F7U Cutlass. There is no evidence of a tip skid in any of the proposal documents or the mockup or the XF7Us themselves.

Similarly, the earliest swept-wing studies at Grumman in 1947 don't feature tip skids and they weren't on the XF10F mockup, which was constructed about the same time as the McDonnell proposals for the F3H in 1948.

My guess is that the tip skid was required on the F3H because of the minimal ground clearance of the tip when the tail skid made contact, even when the wings were level.
(Yes, that is a Mk 7 on the fuselage pylon.)

There was no assurance that the wings would be level in a tip back situation, particularly in the event of a barricade arrestment.

Hence the need for a tip skid on the F3H.

Thursday, February 5, 2015

Goodyear F2G Corsair: Kamikaze Killer?

The F2G was a Corsair developed by Goodyear and powered by the Pratt & Whitney R-4360, a four-row, 28-cylinder radial engine instead of the R-2800, two-row, 18-cylinder engine of the stock Corsair, roughly a 50% increase in horsepower.

It is usually written that the F2G was created to counter the Kamikaze tactic that the Japanese introduced in the Pacific, first recognized in October 1944. If so, someone was prescient, since the decision to install an R-4360 in the Corsair had been made well before that. Pratt & Whitney used two F4U-1s for R-4360 for engine testing. The first one was for ground runs only, which began in May 1943. The second first flew on 12 September 1943.This picture was taken to illustrate the difference between the R-4360 configuration (referred to as F4U-1 WM for Wasp Major) and the R-2800 one:

Goodyear got a contract in March 1944 for 418 F2G-1s and 10 F2G-2s. The -2s were to be fully carrier-basing compatible. Don Armstrong flew the first FG modified with the R-4360 on 26 August 1944. So strictly speaking, the F2G's raison d'etre was not to counter the Kamikaze tactic, at least not originally. (My tongue-in-cheek explanation is that someone in BuAer wondered how fast a Corsair would go when powered by the humongous R-4360.) The F2G apparently was really intended to be supplied to shore-based Marine squadrons, as almost all of the order was for the -1 that didn't have a tail hook or powered folding wings.

In any event, only 10 F2Gs—five land-based -1s like BuNo 88454 in the first picture and five carrier-capable -2s—were built along with several Corsairs modified for flight test of the configuration. The Navy had elected to equip itself with the Grumman F8F Bearcat instead.

One XF2G was flown with a lower aspect-ratio vertical fin that replaced the side area lost by the change to the upper aft fuselage to accommodate the bubble canopy. (The rudder was not changed.)

Goodyear decided instead to add a 12-inch plug to the bottom of the fin, which also provided for the addition of an auxiliary rudder for additional yaw-control power during a waveoff or go-around at low speed.
The auxiliary rudder deflected 12.5 degrees right when the flaps were more than 30 degrees down. (Full flaps was 50 degrees; recommended takeoff flaps was 20 degrees.) The main rudder deflected 7 more degrees to the right than to the left.

Note that the picture on the left is an early F2G-1, which were delivered without a tail hook; the picture on the right is an F2G-2.