Tailhook Topics

by Tommy H. Thomason

Wednesday, April 12, 2017

Things Under Wings: Air-Start Pod

From the August 1956 issue of Popular Mechanics:
 Also see http://thanlont.blogspot.com/2012/01/portable-air-start-cart.html

Ground support equipment will add interest to the display of an airplane model, particularly when it is little known and as beautifully rendered in resin and photo-etched parts as this 1/72 kit, #7019,  produced by F4Models.

 As built (decals not included) and photographed by Alexander Suvorov of F4Models:

The kit includes a resin air hose and instructions on how to permanently bend it to the configuration desired for display.

For more information on this kit and ground support equipment kits available from F4Models, click here: http://f4models.blogspot.com/

Note that these kits must be ordered from Hannants, MisterKit, or Martola.

Monday, April 10, 2017

The Last Propeller-Pulled Corsairs: F4U-5/AU-1/F4U-7

This is a work in progress, updated on 13 April. As usual, comments, corrections, and additions are welcome.

Also, for additional information, see the books recommended in this post: http://tailspintopics.blogspot.com/2011/06/brief-f4u-corsair-oriented-history-of.html

As a hedge against the failure of its transition to carrier-based jets or delays in their availability, the U.S. Navy contracted with Vought for yet another variant of the Corsair, the F4U-5. (For modeler's notes on the F4U-4, see http://tailspintopics.blogspot.com/2014/03/f4u-4-modelers-notes.html.)

The major change was the engine, the Pratt & Whitney R-2800-32W with dual side-mounted, automatically controlled auxiliary stage superchargers. It developed 2,300 horsepower at sea level for takeoff. The combat rating with water injection (from a 28-gallon tank) was 2,700 horsepower at sea level.
The following illustrations are is an overlay of the F4U-5 SAC drawing on the F4U-4 SAC drawing. The installation of the -32W resulted in the most notable changes. First, because of the added length of the auxiliary superchargers and the horsepower increased it was located about 10 inches farther forward and mounted at a nose-down angle of 2.75 degrees. The upper side of the cowling was refaired to take advantage of the downward tilt of the thrust line and therefore provide the same over-the-nose visibility.

Second, the F4U-4's chin inlet was deleted in favor of two cheek inlets at four and eight o'clock (not depicted on this front view) that provided air to the auxiliary air superchargers aft of the engine. The ducts between the inlet and the supercharger required a widening of the lower side of the cowling so it had an pear-shape and flatter bottom when viewed from the front.

 The basic shape of the fuselage from the firewall aft was unchanged.
 Forward of the firewall, the cowling was wider, with a slight but perceptible outward kink in the fuselage at the side of the firewall.

The configuration of the cowl flaps and exhaust collector was also different due to the presence of the ducts between the cheek inlets and the auxiliary air superchargers. The exhaust indentation on the side of the fuselage was located higher than on the F4U-4 (note that there were variations in the exhaust stack configuration). The cowl flaps no longer extended down the entire side of the fuselage. Instead they ended about half way down and the bottom cowl flaps were reinstated that had been eliminated on the F4U-4. There were fewer turning vanes in the wing root inlet.

The propeller was slightly different, primarily thinner (not narrower) tips.

The arresting hook was no longer hydraulically raised and lowered. It simply dropped when released. After landing, a hook man had to manually raise it to a park position for taxi, which was somewhat lower than its latched-up position. When the pilot raised the landing gear after the next takeoff, it was raised to a latched-up position by the retracting tail wheel.

Other changes were the replacement of the fabric on the outboard wing panel with sheet metal and the addition of an avionics compartment access door on the right side of the fuselage aft of the pilot's seat.
A 2,000-lb capacity center-line pylon was added between the two center wing section pylons. The armament was basically the same as the F4U-4B: four 20 mm cannon and eight rocket pylons (Mark 9 Mod 3). Spring tabs were provided on the elevator and rudder controls for lower stick and rudder forces. The catapult hooks were relocated slightly forward and the arresting hook shank was beefed up for the higher gross weight.

Pilot access to the cockpit was improved over the -4's by adding a telescoping step below the folding step in the side of the fuselage (it is extended in the photo above). These were actuated by a cable connected to the tail wheel but could also be closed and opened by deck personnel. The seat was a bucket type with folding arm rests. The center console was eliminated below the instrument panel to allow the pilot to stretch his legs on long flight. The manual hydraulic pump was deleted in favor of an electrically driven auxiliary hydraulic pump. There were some detail changes from the -4, e.g. the arresting-hook and wing-fold controls were moved to the right side of the cockpit. The top of the canopy was raised similar to the late production -4s, with a fairing added to the top of the turtle deck aft of the cockpit. The gun sight was one of the first lead-computing designs, the Mark 6 Mod 0 gunfire control system (with a Mark 8 gun sight) that also incorporated rocket aiming capability.

The F4U-5 was produced in three flavors: basic -5 fighter; -5N night fighter with an autopilot, Mk 20 illuminated sight, and a radar pod on the right wing; and -5P photo-reconnaissance with camera ports on both sides and the belly as well as a small fairing on the fin leading edge for the relocated compass transmitter.

In addition to the radar pod, the F4U-5N external features were a glare shield over the upper engine exhaust stacks, which were all fitted with flame suppressors as well; flash suppressors on the cannon barrels; and additional antennas. A gun-camera light/flash guard was sometimes added.

This F4U-5N has also been equipped with the wing and empennage deicing boots.

The F4U-5P camera ports were fitted with sliding covers:

A hatch was also added to the turtle deck (with a foldable ladder that was stowed in the top of the compartment) for access to the cameras:

The AU-1 was a Corsair tailored for Marine Corps close-air support, provided to them as a placeholder in lieu of AD Skyraiders. (Also see http://thanlont.blogspot.com/2009/03/f4u-corsair.html.)
Originally designated the F4U-6, it was a minimal modification of the F4U-5 optimized for low-altitude performance, incorporating increased protection from flak and small arms fire, and providing more stores options. Since it did not need high-altitude capability, the big auxiliary stage superchargers were removed with the installation of a R-2800-83WA with single-stage supercharging. A new cowl ring without cheek inlets was installed but the pear-shaped cowling remained since the F4U-5 tooling was used. The oil coolers were turned 90 degrees and moved inboard.
Armor was added to the underside of the fuselage and the cockpit.

Because the oil coolers had been moved into the fuselage, there were only turning vanes in the air inlet in the wing leading edge. For some reason, possibly to reduce the glare from the exhaust stacks at night that had been a shortcoming of the -5, the exhaust indentation on the side of the fuselage was located lower than the F4U-5's (this was possible because the ducting between the -5's chin inlets and superchargers had been removed). The cowl flap configuration remained the same.

Five multi-purpose pylons were provided on each outboard wing panel in place of the four rocket pylons of the -4/5.
The wing center-section pylons were subsequently increased to carry 2,000 lb stores.

Finally, the French need some new fighters for their aircraft carriers that were too small to operate jets. Since the Corsair was the best candidate, the AU-1 configuration then in production was adapted for the mission and designated the F4U-7. Note that the armament on the outboard wing panel is identical to the AU's.
Note that the tail hook is in the "park" position. See the French AU-1 picture below for the "latch" position. 

The major difference was the need for a high-altitude capability, which was provided by installing a two-stage supercharged R-2800 engine, reportedly from surplus F4U-4 inventory. However, the fuselage was the same as the AU-1's with the exception that a new cowl ring was incorporated that had a chin inlet to supply air to an F4U-7-unique oil-cooler installation. Note the beginning of the cowling bulge at the firewall that was common to the F4U-5/AU-1/F4U-7.
 Photo via Jim Sullivan

 Like the AU-1 wing root inlet, the F4U-7's only contained turning vanes but in a different configuration because of the different utilization of the air. This is my current guess at its configuration.

Since it was built using F4U-5/AU-1 tooling, and this is an important distinction, the lower forward fuselage remained pear-shaped up to and including the aft side of the cowl ring.

There is understandably some confusion about the detailed differences between the AU-1 and F4U-7 configuration. For one thing, the French were provided with some Marine AU-1s straight from Korea. As a result, there are blue French-marked Corsairs that are not F4U-7s but AU-1s, the main difference being the lack of a chin inlet.
 AU-1 129391 14 Flotille Cuers NAB 17 March 1964 via Jim Sullivan

Another is that the Corsair marked as a USMC VMA-212 AU-1, including BuNo, at the USS Alabama Battleship Memorial Park in Mobile, Alabama was actually a former French F4U-7;  the -7 cowl was subsequently replaced with an AU-1's, which still left miscellaneous antennas as configuration anomalies. It is now on display at the San Diego Air & Space Museum, again as an AU-1.

And the French F4U-7 war bird featured in a walk-around photo collection here: http://www.arcair.com/awa01/601-700/awa689-Corsair-Salaun/00.shtm is reportedly a converted F4U-5N. Its authentic cowl (note the bulge and chin inlet) reportedly came from the F4U-7 that was on display at Mobile, Alabama.

More later...

Saturday, March 11, 2017

F2H-3/4 Tip Tanks

I turn out to be wrong yet again. I knew that the F2H-3/4 tip tanks had a capacity of only 170 gallons compared to the -2's capacity of 220 gallons and therefore imagined that the -3/4 tanks were smaller. It sort of looks that way.


My guess is that the -3/4 tanks appear to be smaller because of the airplane's longer forward fuselage and tail cone and the increase in wing chord inboard of the fold line. However, I'm now all but certain that the tanks are the same size and shape. They are different, however. The -2 tank was mostly fuel; the -3/4 tank was comprised of what I'll call a capsule, with fairings added on the front and back, so it held less fuel. The only notable external difference was that it had prominent flanges and fewer filler caps/access panels.
Another feature shared with the -2 was that a tank could be installed on either wing tip without modification. That's why there are filler caps on both the top and bottom of an installed tank and two position lights on the nose of the tank, one for red and one for green depending on which side it is installed.
Note that the F2H wings could not be spread or folded with full tip tanks so the filler caps had to be at top dead center when the wings were spread regardless of which side the tank was mounted.

Because it had more internal fuel and smaller capacity tip tanks, the F2H-3/4 was often seen without tip tanks. A smooth wing tip could also be installed in place of the one on which the tank was mounted.

For modeling notes on the Banshee family, see http://tailspintopics.blogspot.com/2009/12/f2h-banshee-modeling-notes.html

Sunday, February 12, 2017

The Complete F-111B Updated

I've just updated my original "The Complete F-111B" post to provide links to recent posts. See

Friday, February 3, 2017

The F-111B Production Main Landing Gear

The Navy was unhappy with the F-111B's tip-back angle. In other words, the main landing gear was too close to the airplane's center of gravity with the wings swept back, so if the brakes were applied while the airplane was being pushed back into a parking spot, the momentum would cause the airplane to tip back. This might also result from the roll of the carrier. And there were dire consequences: it might result in the airplane and brake rider being lost over the side if the tail skid was past the deck edge.

One early solution was a moment-carrying tow bar to move the cg forward. It was evaluated but determined to be inadequate, not to mention awkward to handle.

The decision for F-111B production was to move the wheels eight-inches farther aft.

I had noted that F-111B landing gear installation had changed at some point early on (probably with 151973 but certainly with 974 and 152714/5) to move the wheels aft.

 (Note that 972 has the early Air Force tires while 715 has the Navy tires. Also see http://tailspintopics.blogspot.com/2009/10/grumman-f-111b.html)

The landing gear was definitely rotated more around the retraction pivot point, moving the wheels aft. However, a rough layout indicated that the shift aft was almost certainly less than eight inches.

Steven Hyre recently posted some F-111B illustrations on his Facebook page, The F-111 Historical Association, that were new to me. One of them was for ECP 1000 and revealed the planned change:
On close inspection of the dashed lines, you'll see that the landing-gear crossbeam has been redesigned to move the axle aft by eight inches. Like the raised cockpit, this was a production change that was not present on 152714 or 715.

Sunday, January 29, 2017

F8U/F-8 Unit Horizontal Tails

Unit Horizontal Tail (UHT) was the Vought term-of-art for the all-moving stabilator. When the F8U-2NE (F-8E) was adapted for the French Navy requirement, the wing was modified with a two-segment leading-edge flap and boundary layer control for a reduction in approach speed.

A new, larger UHT was required as a result. When the U.S. Navy upgraded some of its F-8Es to the F-8J configuration, this wing and horizontal tail was used to accommodate the increase in gross weight.

Thanks to Tom (Superheat) Weinel and Vought data, I'm finally able to create a pretty good illustration showing not only a size comparison of the larger horizontal tail but where it was located on the fuselage relative to the original one.
There are reports that the change was accomplished simply by adding a leading edge cuff. I'm pretty sure that the cuff in question was incorporated to protect the leading edge from the blast of fuselage-mounted rockets and missiles, not to enlarge the UHT.

Although the UHT was mounted with dihedral of 5° 25', I was unable to determine if the spans given were actual (tip to tip when attached), or of the UHT without dihedral. My guess is that the span was with no dihedral, which is how I created the illustration above. In any event, the difference in span is only about 1/2 inch.

For a summary of F8U/F-8 differences, see http://tailspintopics.blogspot.com/2009/10/f8u-crusader-variations.html

Monday, January 23, 2017

The F-111B Auxiliary Flap

24 January 2017: Updated with additional information and a photo.

Steven Hyre recently posted some excellent exploded views of the F-111 wing on his Facebook page, The F-111 Historical Association. One of them reminded me that I was still hoping to find a picture of the F-111 auxiliary flap.
It was a small flap added inboard of the existing flaps in the narrow space between the most inboard of them and the fuselage. It was electrically actuated separately from the original hydraulically actuated flap system and could only be extended when the wing was swept fully forward. As shown on the drawing above, it was effective on "Navy 6" and above, which meant BuNo 152714 and subsequent F-111Bs.
Given its small size, it is apparent that Grumman was grasping at every opportunity to increase lift and reduce the nose-down attitude of the F-111B on approach.

The production F-111B flight manual describes it in some detail. Extension and retraction were automatic but subject to limitations, e.g. it would only extend if the wings were full forward and the wing flaps were extended 28 degrees or more.

However, I had never seen any photographic evidence of it. Here are a couple of closeups of the inboard section of the wing of "Navy 6" with the flaps down.

Now it's possible that the wing in the first picture above is not fully unswept but it would appear that it is in the picture below it (note how close the wing leading edge is to the lower door of the rotating glove installation). In any event, no auxiliary flap is apparent in either one.

Posting a request for information on the F-111 Historical Association Faeebook page quickly resulted in some. Steven Hyre noted that a USAF tech instruction was issued in October 1968 to deactivate the auxiliary flap on F-111As and Cs and FB-111s, which was very early on in the F-111 program, e.g. the first production FB-111 first flew on 13 June 1968 and the first F-111C flew in July 1968 (and promptly disappeared into long-term storage). The extension limits and early deactivation explain its rare appearance in photographs.

Kevin Morrison wrote that the auxiliary flap was disconnected because it was tearing up the lower fairing seal of the fuselage opening into which the wing trailing edge swept. Bill Lassiter remembers that the lift benefit was pretty limited and there was concern that the need to first retract the auxiliary flap might delay an urgent need to sweep the wings from full forward for whatever reason.

And best of all, Patrick Flohe provided the following closeup of the auxiliary flap lowered on an F-111A.

He also noted that at the time the photo was taken, this airplane still had the original aft main landing gear door that opened parallel to the bottom of the fuselage.