McDonnell F3H Demon Nose Landing Gear

Most landing gears consist of an oleo or cylinder mounted to aircraft structure and a piston on which the wheel is mounted. The piston functions as a shock absorber. The two are connected with a mechanism that does not allow the piston to twist within the oleo. Often that is a torque link or scissors.

The scissors on the F3H nose landing gear is more complicated than usual because it also provides the means to shrink the unit to fit in a shorter wheel well. Instead of two links, there are three. Two shrink struts, one on each side of the scissors, pull the piston up as the nose landing gear is retracted. Note that the right-hand shrink strut, but not the left-hand,  has a bend in it to provide clearance with the landing gear strut and the lower end of the middle link extends beyond its connection to the lower link.

The shrink link is angled slightly downward and does not move as the piston absorbs the shock of landing. The middle and lower links keep the oleo and the piston aligned.

However, as the landing gear is retracted, the location of the upper mounting point of the shrink struts ahead of the mounting point of the landing gear strut causes the shrink link to be rotated upward to be parallel to and lie against the oleo. Since the pivot point between the shrink link and the middle link has moved up, the middle link moves up, pulling the lower link and the piston with it, shortening the nose landing gear assembly.

The lower section of the middle link that extends beyond the pivot point either keeps the scissors from over-centering or takes some of the load off the pivot point, possibly both.

Grumman S2F/WF/TF Engine Nacelle Detail

Every once in a while someone asks a simple question about an airplane I happen to know quite a lot about and I don't know the answer. In this case, it was the engine exhaust system on the Grumman S2F/WF/TF (S-2/E-1/C-1). The upper exhausts are obvious (this is a picture of an early S2F-1):

The question basically was, did the exhaust gas from all of the cylinders come out here or were there other exhaust stacks on the nacelle. You'd think the answer would have been included in the S2F monograph that I wrote with Bob Kowalski (see http://tommythomason.com/books/grumman-s2f/). It wasn't.

It turns out that in addition to the two troughs on the top of the nacelle there was a third, virtually identical one located on the bottom of the nacelle:

It ended at the forward edge of the oil cooler door. Note the convex stiffener running longitudinally down the center of the trough. The oil cooler door is open in the following picture:

My guess is that there were also two pipes located here that were the exhaust system for the lower four cylinders of the Wright engine.

This is an illustration of some of the engine nacelle panels:

Item 11 is the panel that includes the lower trough. Item 10 is the oil cooler exit and door. Item 4 is one of the two upper troughs (5 is an insulation blanket).

Interestingly, this trough is represented on the ancient Hasegawa 1/72nd S2F kit, another example of its high level of accuracy particularly compared to the much newer 1/48th kit from a different manufacturer...

Grumman F9F Panther/Cougar Canopy

The Panther and Cougar canopies were basically the same from a structural standpoint and the defrost system, which was not initially on the very early Panthers. The frame detail (white fiberglass reinforcement) changed over time and a radio antenna was added on the inside of the canopy on a separate sheet of Plexiglas.

Note the canopy's internal structure that arched over the canopy actuator. Its forward edge was slanted so it butted up against the armor plate when the canopy was closed.

The defrost duct was open on its forward end when the canopy was open; when the canopy was closed, it connected to a supply hose on the aft cockpit bulkhead alongside the ejection seat.

The red insulated hose assembly teed off at its aft end to supply defrost air to two tubes, one for each side of the canopy.

Color photos of the F9F-6 at the National Naval Aviation Museum by Don Hinton

Not shown on the airplane above is an electrical cord on the right side of the canopy that connects to the antenna on the underside of the aft end of the canopy glass. It is fully extended in this picture of an F9F-2. (Note that the headrest is angled forward, which is why the "rope" handles that pull down the face curtain are not laying on the front of the headrest.)

This shows the electrical cord, defrost hose, and other components mounted on the aft bulkhead of the cockpit of an F9F-5 (the other Panthers are similar if not identical).

Droppable Survival Kits

Because of the harsh Korean weather in winter during the Korean War, droppable survival kits were developed, with one aircraft in a strike carrying one. This is an example.

Republic F-84 Thunderjet Fuselage Length

I can't remember why I did this illustration of the fuselage difference between the F-84A/B/C/D and the F-84E/F or who I did it for, but it was a typical update to early jets to provide better range and/or endurance, although in this case, given the relatively small increase in fuselage fuel capacity (36 gallons), it might have been a center of gravity adjustment:

Note that the fuselage change also involved different fairings at the wing root, access panels, etc.

The differences among the F-84s over time was extensive. The ejector around the engine tailpipe changed along with changes in the tail-light installation and the ventral-fin fairing. The pitot tube was in difference places, the landing gear doors were redesigned for the D and its landing gear compression mechanism changed from hydraulic to mechanical, etc.

The go-to guy for the F-84 was Bruce Craig but his web site appears to have gone walkabout.

F-18A Main Landing Gear

Bell P-39 Wing Planform

In my post on the Bell XFL-1 (see https://tailspintopics.blogspot.com/2015/09/modeling-bell-xfl-1-airabonita.html), I included a sketch to show the difference between the P-39 and XFL-1 wings. It was created before I had become proficient with Illustrator and regretably, I wasn't very rigorous about the shape of the P-39 wing (the XFL-1's is pretty good but I'll redo that illustration in the near future).

It turns out that some modelers gave me more credit for the drawing's accuracy that it deserves and lacking a better one of the P-39, have used it to evaluate the wings in various Airacobra kits. As a result, I have created a pretty accurate drawing of the planform using Bell data and a piece of a Bell P-39 drawing in my collection.

Wing planforms are generally defined by span, root and tip chords, and the location of the root and tip chords along a span-wise line. Usually the root chord is located at the aircraft centerline for the benefit of the aerodynamicists but not in the case of the P-39. It was located at the side of body, which is where non-aeronautical engineers would think the root chord would be. The span-wise line in the case of the P-39 is perpendicular to the centerline and at 30% chord. That data establishes the location of the leading and trailing edges. The tip can be defined in different ways; based on an XFL-1 wind-tunnel model drawing, it was probably a portion of a pair of circles that were faired into the leading and trailing edges. Unfortunately, I did not have a drawing with that data but I did have a Bell drawing of the Model 4A wing tip that is probably close to right. On the other hand, the shape of the aileron is iffy; I don't have a Bell drawing for it and the ones on the internet differ.

Note that I didn't correct for dihedral or incidence but those would be very small differences. 100" is given as the root chord for the Model 4 proposal (and a wing span of 35'), the P-39E and the XFL-1. In the case of the latter, however, it is located at 17" from the centerline and might therefore be consistent with the P-39D root chord value.