Tuesday, November 24, 2015

What's Under the AD Skyraider Canopy?

I have wondered exactly what was behind the headrest of the AD Skyraider canopy. It looked like a tan canvas-like cover that angled down from the top of the headrest to the top of the fuselage just before the aft end of the canopy. And that's just what it appears to be.

The deck behind the headrest is actually the top of the fuselage. The canopy slides on three rails, one on each side of the cockpit and one on the top of the fuselage.

The sliding canopy was powered.
That mechanism appears to be the only hardware under the sliding canopy. Note the "boot" that enclosed the mechanism. It appears to have a closure at the top over the air-to-oil transfer cylinder.

Early Skyraiders did not have the boot.

It appears that it was added to ensure that a leak from the mechanism would not be sprayed into the cockpit enclosure. The boot was not always in place.
The armor plate and seat arrangement (note that the canopy actuation mechanism is not shown).

The headrest that was attached to the armor plate could be tilted forward. Some other pictures;

Saturday, November 7, 2015

KittyHawk XF5U

Kitty Hawk has just released an unusual choice for a plastic model kit, the Vought XF5U-1, in 1/48 scale.

The prototype never actually flew, having been overtaken by jets while it was being designed and built. For a brief history on the program, see http://thanlont.blogspot.com/2012/07/missed-it-by-that-much.html

Here are a few notes on the configuration of the prototype that might be of interest in building the kit.

There are pictures of the prototype before markings were added to the vertical fin.

Some of the few pictures that exist are in a ground-run configuration. Although self-boarding steps were provided, a set of wooden steps were used for ease of accessibility to the cockpit and maintenance-access panels.
A closeup of the temporary and self-boarding steps.

These self-boarding steps are accurately represented on the kit parts based on this built model.
Note, however, that the direction of rotation of the propellers is incorrect on this model.

Handrails were provided for ground run.

The model pictured above doesn't show the prominent cowl flaps and the second set of flaps behind them but the actual kit appears to provide at least separate cowl flaps. (Note that the left-hand flap behind the cowl flap is missing in the following picture.)

This wind-tunnel model included both sets of flaps.

The cowl flaps were repeated on the bottom of the fuselage along with a third cooler outlet flap under the center of the "fuselage".

The tip of the nose was clear because it was intended that a gun camera and approach light be located there.
This drive-train illustration provides an indication as to the location of the coolers:

The tailhook mechanism depicted on the built model looks a little off to me. Here is a annotated diagram from the Vought maintenance instructions.

Note that the tailhook was not installed on the prototype.
Note the location of the steps and the position of the cooling flaps.

A closeup of the pitch and roll control surface (the flaps in the afterbody were for trim).

The best single reference for the XF5U is, as usual, from Steve Ginter.
It can be ordered directly from him: http://www.ginterbooks.com/NAVAL/NF21.htm

Thursday, July 23, 2015

Douglas AD (A-1) Skyraider Pylons

The configuration and orientation of Skyraider weapons pylons comes up from time to time. They are usually not depicted correctly in model kits. This is a work in progress.

The pylon on the inboard wing was perpendicular, i.e. hanging straight down (except on the unique pylon for the big podded radar: see http://tailhooktopics.blogspot.com/2012/11/ad-4n-aps-31-radar-pod.html). The pylons on the outboard wing panel were perpendicular to the wing instead; they were also not evenly spaced.
The view from the side.

The outboard wing pylons were also not "swept" at the same angle as the leading edge, i.e. the most outboard one was closer to the wing leading edge than the most inboard.

The center-line pylon on the later ADs:

Note the interface with the oil cooler outlet: the forward end of the pylon is much deeper because it sweeps up into the duct (don't be mislead by the shadow).
 I'm told that the Trumpeter 1/32 center pylon does not angle upward from front to rear as it should.

Early ADs had much smaller and less capable AERO pylons on the outboard wing panel. See http://tailhooktopics.blogspot.com/2013/12/things-under-wings-aero-pylons.html

AD-1s through -4s had a smaller inboard wing pylon than the 5/6/7. The later, longer pylon introduced on the -5 was reportedly necessary to move certain stores farther forward for ground clearance. It also added provisions for the 30-inch lug spacing required for some stores. In addition, it may have been desirable to move the loaded center of gravity forward, particularly on the -5.
Thanks to Ed Barthelmes for a pretty good drawing of the early pylon. However, it has been hard to pin down the exact location of the early pylon on the wing from available drawings. The above drawing is my best guess at the moment.

Here is a direct comparison of the World War II era 1,000 and 2,000 lb bombs on the earlier pylon.
Early ADs did not have an external center pylon so that a torpedo could be carried. The shackle was mounted within the fuselage along with provisions for an explosive cartridge that propelled a bomb downward away from the airplane when dive bombing so that it would not hit the propeller.
Illustration from Ed Barthelmes

As a result, the bomb or torpedo was snugged up directly beneath the fuselage.
U.S. Navy via Steve Ginter

Wednesday, July 15, 2015

F6F-5K Drone Strike, Korea

For background on this and the F6F drone program in general, see http://tailspintopics.blogspot.com/2009/11/f6f-drones.html.

Note that the bomb has not tail fins (it's not going to be dropped), the F6F does not have the F6F-5K tailwheel extension (it's not coming back), and the additional antennas for remote control and television picture transmission.

Saturday, May 16, 2015

Special Hobby AF Question

A question was raised about the length of the cowling based on a photograph of a Grumman AF model built from the recently released Special Hobby 1/48th kit, specifically whether it looked a little short. (http://www.britmodeller.com/forums/index.php?/topic/234981898-new-148-grumman-guardian-by-special-hobby/)

Based on a pretty good Grumman three-view, which compared quite well to the Grumman fuselage station data, I calculated that the distance between the leading edge of the wing at the fuselage and the forward edge of the cowling at the fuselage reference line (where the propeller shaft extends), should be 69 mm or about 2 3/4 inches. The kit dimension was subsequently reported to be 65-66 mm.

At that point, I double checked my scaling of the fuselage station drawing (good only for length, not shape, particularly the vertical fin in this instance) and the Grumman three-view and added the AF Standard Aircraft Characteristics side view for comparison. All the drawings compared well in length, with the clear exception being that the wing on the SAC side view was about 3 mm farther forward than on the other two drawings.

I cropped the above to illustrate the difference between the SAC wing location and that of the other two drawings.
It's possible that Special Hobby relied on the SAC sideview for the wing location.

The perceived discrepancy in the picture of the model is likely exaggerated by the camera.

Wednesday, April 29, 2015

ESCI 1/48th FJ-2/3

29 October 2016: It turns out that I was wrong about being wrong with respect to the FJ-4 horizontal tail so I revised the top view drawing at the bottom of this post. Thanks to maintenance manual data provided by Frank Truchi, a volunteer at the National Naval Aviation Museum, I now know that the production FJ-4 horizontal tail leading edge was swept at 35°. The NAA drawing of the horizontal tail is therefore accurate except for the span.  (Also see http://tailspintopics.blogspot.com/2016/10/north-american-fj-44b-fury-notes.html.)

Some people are desperate for a good injection-molded kit of the North American FJ-2/3 Fury, so desperate that they consider building the ESCI 1/48th kit. While I'm sure that a fairly accurate model can be built from it, some changes will be necessary.

The most notable errors are in the forward fuselage,
as detailed here:
Note that the ejection seat is located too low and far aft in the cockpit.

It fairs even worse as an FJ-3, because its inlet was even deeper. (And that scoop on the aft fuselage needs to be cut down and a recessed ramp added ahead of it.)
Note that the aft nose landing gear door is not wide enough.

Since the bottom of the sliding canopy has the distinctive "dip" of the FJ-2/3's at its forward end (added to allow the pilot to sit higher for takeoff and landing while closing and opening the canopy) and the inlet is an undersized version of the FJ-2's, it doesn't make for a good XFJ-2 out of the box either. The XFJ-2 had the standard F-86 sliding canopy with a modified windscreen for better over-the-nose visibility. For an overview of the North American FJ Fury family, see http://tailspintopics.blogspot.com/2009/10/fj-fury.html

However, even given its shortcomings, the kit has possibilities. Deepening the forward fuselage wouldn't be too difficult. "Impatient Pete" modified an F-86 with this cut on the way to an FJ Fury in an ARC forums post.

The bottom of the windscreen and sliding canopy could possibly be filed down to lower them to the right height. A F-86 canopy might be even better.

I don't have the kit so I can't say what has to be done to the wings, horizontal stabilizer, etc to improve its accuracy. For those details, see http://tailspintopics.blogspot.com/2011/04/fj23-fury-redux.html

While most of us are content to imagine the possibilities or hope for a new FJ-3 kit, Jon Kunac-Tabinor has not only sallied forth with the Esci kit, he is posting his progress here: http://www.britmodeller.com/forums/index.php?/topic/234981173-north-american-fj-3-fury-148th-esci-with-added-elbow-grease/#

However, Jon is having trouble with the quality of Esci plastic and Bob Sikkel reports that the Esci wing has the incorrect sweep and aileron location. The desperate might want to consider another 1/48th scale alternative, a mash up of the Grand Phoenix FJ-4 and a Monogram F-86.  The FJ-4's fuselage was very similar to the FJ-3's (see Jon Krol's comments below and the following illustrations). Bob Sikkel also provided the following comparison of 1/48th kit inlets to which I've added photographs of the actual airplanes.
Somebody has measured the FJ-4 at Tyler, Texas as having an inlet width and height at the location of the inlet plug of 23".

The FJ-3 and FJ-4 fuselages were almost identical, except of course where it is obvious that they aren't as well as the small difference in downward angle of the 20 mm guns. While the main landing gear was very different, the nose gear appeared to be the same except that the shock strut was more extended at rest.
Note that the North American draftsman had to wing it with details like access panels, speed brakes, etc. (obvious when comparing the FJ-3 and FJ-4 side views) so there may be some variation in their location from the above. Your guess is as good as mine on the vertical fin: were the leading and trailing edges different or not?

The wings and horizontal tails were very different, which is where an F-86 kit is required.

Note the difference in span between the prototype and production FJ-4 horizontal tails: