Tailhook Topics Drafts

Monday, May 14, 2018

EKA-3B Aft Fuselage

Yet another question about the accuracy of the Trumpeter 1/48 A-3 Skywarrior kit has been brought to my attention, in this case the location of the main landing gear wheel well, which is reportedly a bit too far aft. Leaving it where it is creates a problem with national insignia placement. Moving it forward 4-5 mm means the big antenna fairing on the aft fuselage now appears to be too short.

One problem with addressing the accuracy of the kit is establishing a baseline from which to determine the proper placement of major details. In this instance, I've shown the location of the trailing edge of the wing on the fuselage, the vertical fin fold joint, the interface of the rudder with the fin, and a few fuselage station locations (in inches from just forward of the tip of the nose).
The outline of the fuselage and the location of the wheel well and the speed brake are from
pretty good Douglas drawings. The location of the antenna pod is from a sketch of unknown provenance. This is from a set of Luc Colin walkaround pictures:

For many more, see http://www.primeportal.net/hangar/luc_colin3/eka-3b_skywarrior_142251/

Sunday, April 8, 2018

NAEL F9F-2KD

By coincidence, I received questions last month from two different modelers about this particular airplane that was a profile in Scale Aircraft Modeler Vol 7 No 5. It was also a subject on Blackbird Models decal sheet BMD 72013.

Unfortunately, some critical information was missing. This was a former F9F-2KD (no BuNo) that had been stricken (no national insignia) but instead of being scrapped, it was transferred to the Navy test facility for Ship Installations, e.g. development of aircraft carrier catapult and arresting systems. Here is a picture of it in a display of a barricade at an open house.
If you look closely at the nose landing gear, it clearly isn't stock. That's because it was used in the development and evaluation of the nose-tow launch system (see http://thanlont.blogspot.com/2011/01/catapult-innovations.html)


Note that it didn't fly away after the catapult stroke since it was no longer airworthy.

Other configuration details: the tip tanks had been removed but they weren't replaced by the wing tip fairings; the fence outboard of the engine inlet is present; and the antenna fairing under the nose cone has either been added or the nose cone from another Panther/Cougar has been substituted.

Paul Bless reminded me that this particular F9F-2 (or a stablemate at NAEL or its nose gear) survived and may still be displayed in a bogus paint scheme at Aviation Heritage Park at NAS Oceana. See http://warbirdsnews.com/warbirds-news/fun-facts/this-day-in-history/happy-birthday-grumman-f9f-panther.html


Thursday, March 1, 2018

FJ-1 Tip Tanks - 1948 Bendix "Race"

Once upon a time, there were big-deal airshows with military participation, including "races". At some point the services were prohibited from competing with each other directly so they took turns year-by-year for the major events. The 1948 Bendix race was to be a Navy year, showcasing the new North American FJ-1 Fury assigned to VF-51. Takeoff was from Long Beach, California with the finish line at Cleveland, Ohio about 2,040 statute miles away.

When I wrote about this event in U.S. Naval Air Superiority, the range and speed numbers originally didn't add up. The FJ-1 cruising at 40,000 feet had a range of about 2,300 miles but almost certainly at a long-range cruise speed of only 350 mph versus the winning speed of 490 mph. However, looking at pictures of the airplanes involved, they clearly had different tip tanks than standard.


They were longer relative to their diameter, didn't have the position light in the tip and also had a rounded aft end and a fore-and-aft horizontal flange. The nose and tail resembled those on a 150-gallon external tank of the time with a longer, bulged center section and the FJ-1 tip tank fins added.

According to a Naval Aviation News article, these bespoke tanks could carry 290 gallons of fuel each versus the standard FJ-1 tip tank capacity of 170 gallons. These enabled the Bendix racers to fly much faster and still get to Cleveland. Just barely. One pilot flamed out 50 miles away from Cleveland at something over 40,000 feet and glided there for a dead-stick landing. The winner flamed out while taxiing in. Another climbed to 50,000 to stretch his fuel (the FJ-1 cockpit was not pressurized), became hypoxic and lost, finally crash landing in a field.

Now misreported most places on the interweb, a California Air National Guard pilot, not officially competing but just going to Cleveland in a P-80C nonstop with nonstandard tip tanks, beat the Navy's best time by a minute or so.

The question has come up as to the size of these non-standard tanks. It can't be directly scaled from the picture above because of the camera lenses distortion of length versus diameter. Knowing the volume proved to be less useful than I hoped. It turns out that the standard 150-gallon tank must have fore and aft voids. Stretching it to add a 140-gallon cylinder results in a tank that looks too long relative to the diameter. I also tried to correct the picture of the tank using the fore and aft sections of the 150-gallon tank, which looks better with respect to length but means the voids had to be eliminated; if retained, the addition only came to about 48 gallons.

The new tank center section did have to accommodate the tip mounting of the FJ-1's as opposed to being slung under a wing on a pylon so it may be that the fore and aft sections were modified to eliminate voids as part of this reconfiguration. This is my best guess at the size and shape:

Tuesday, February 27, 2018

FJ-1 Fury Canopy

Initial open/close mechanism:




Later open/close mechanism:



Wednesday, January 10, 2018

The Grumman XF9F-9, Too Little, Too Soon

After the debacle of the XF10F Jaguar and the hasty conversion of the straight-wing F9F Panther to the swept-wing F9F Cougar, Grumman elected to propose the jet-powered equivalent of their F8F Bearcat to the Navy, encouraged to do so by BuAer's Fighter Class Desk. It was to be light, simple, inexpensive, maneuverable, and capable of near sonic speed in level flight without an afterburner. The engine selected was the Wright J65, a license-built British Armstrong Siddeley Sapphire that had also been selected to power the Navy's FJ-3 Fury and A4D Skyhawk. At the last moment, BuAer decided to add an afterburner in this instance.

Wright experienced difficulty in qualifying the afterburner so the first XF9F-9 made its first flight without one (it was subsequently redesignated F11F Tiger, since it bore no resemblance to its F9F Cougar forebear even in a dim light).

Like the Bearcat, it was relatively small and would have been wrapped snugly around its engine except that it was snugly wrapped with fuel tanks, not enough as it turned out.




Unfortunately, the F11F not only proved to be too small, lacking endurance, it was too soon, since the General Electric J79 then in development subsequently exceeded expectations as the afterburning Wright J65 was falling short of them. When evaluated with the J79, the F11F not only had terrific performance, it had somewhat better endurance. By then however, the Vought F8U Crusader had enough of a head start that the little Tiger became an also-ran.

A model of the first-flight prototype would be a relatively straight-forward conversion of a production F11F since most of the airframe was unchanged.
Note that the nose is even shorter than the original production F11F's but the wings, horizontal tail, and much of the fuselage is the same (the extreme aft fuselage has to be reshaped and shortened). Deletions include the wing fillet on the second production lot airplanes and the splitter plate ahead of the inlet (the inlet was offset from the fuselage, however). The vertical tail is smaller. Some other notable differences are the large pitot on the right side of the forward fuselage (it was subsequently moved to the vertical fin), the nose-landing-gear doors, the size of the wing fence, and the leading edge slat arrangement.



Another option, in 1/48, is the old Lindberg kit: https://www.britmodeller.com/forums/index.php?/topic/235037783-f11-f-tiger-ever-build-one-of-these/

Wednesday, October 25, 2017

FJ-2/3 Nose Landing Gear

Warning: Probably more than you want to know!

First an overview of the nose landing gear from the side.
Note that the shock strut is angled slightly forward and the yoke is mounted in front side of it. The anti-torque scissors on the right side of the strut is angled somewhat aft. The Sword assembly illustration would have you mount the yoke on the bottom of the strut and have the scissors angle forward. Paul Boyer also noted that it would have you put the shimmy damper and the anti-torque scissors on the wrong sides.

This is a closeup of the interface between the strut and the yoke;
Craig Kaston photo

Note that there is a shimmy damper mounted on the left side of cylinder that the yoke is mounted under. It turns out that the yoke is free to rotate within that cylinder since it is basically a sleeve ( there is no nose-gear steering; the pilot steered during taxi and the first part of takeoff and the last part of landing with the brakes).
The shimmy damper does not turn with the nose wheel; it is connected to the yoke where it protrudes at the top of cylinder. What confused me at first looking at pictures of FJs in museums was that lever extending aft on the left side of the yoke. At first I assumed that the museum had left something off but I finally realized that the shiny cylinder at the end of that lever contacted some kind of "ramp" in the nose-wheel well as it was going into the well that turned the wheel 90 degrees so it lay flat under the inlet duct. (On the F-86 that was done with an actuator.) Presumably the shimmy damper provides a centering function when the landing gear is extended.

The line coming down from the wheel well to the bottom of the shock strut pressurizes it to raise the nose for a catapult takeoff. However, the actual routing, at least early on, is along the scissors as shown on this early production (a few were blue) FJ-2:

Here is a comparison of the "normal" strut extension and pressurized for a catapult launch:
However, the strut might be somewhat or fully extended at other times for various reasons.

The Sword nose landing gear strut appears to be too long. I assembled the three big pieces. I drilled an .080 hole in the cylinder in front of the strut and in the yoke to pin them together with a piece of wire since I think simply gluing them won't be sturdy enough.
It looks like I'll need to cut off that thicker section at the top of the strut and "flatten" the tire a bit to get closer to the right "sit". The yoke is also too long but shortening it looks like to much work.