by Tommy H. Thomason

Sunday, August 25, 2013

Things Under Wings - Sparrow Missiles

This is another one of those works in progress that I'll have to update and correct. But in the meantime, one or two people are looking for pretty good dimensioned drawings of the Sparrow I.

The Sparrow "family" of missiles began with the Navy's desire to use guided missiles for air defense of its carriers. The first Sparrow was a so-called beam rider. The pilot aimed the plane's radar at a target and launched the missile, which was equipped with rearward facing antennas that detected the radar beam. The missile control system used that input to continually correct the Sparrow's direction of flight so as to stay more or less in the center of the beam and arrive close enough to the designated target for its proximity fusing to detonate its warhead (sort of a misnomer since it was actually located in the middle of the missile).

Various lengths for the Sparrow I can be found on the interweb but I'm relying on Craig Kaston's detailed measurement of the one at the Pt. Mugu museum for the above drawing. Note the sharply pointed nose for high speed flight, possible because the antennas were facing aft, not forward.

Craig also provided pictures of the forward fins, which provided the flight control, and the antenna fairings between the aft fins, which were fixed.

The Sparrow I failed to meet expectations. It was more or less operationally employed on the F3D-2M (the Skyknight was also used for much of its development as well), the F7U-3M Cutlass, and the F3H-2M Demon, but for only a year or two in each case.

VX-4 F3D-2M, Project Steam:

VX-4 F7U-3M shipboard evaluation:
 Note the flare installation at the aft end of the missile.
I'm not sure what this was for. It may have been to provide visual tracking after the rocket motor burnout to get the missile back under control if it had not captured the beam after being launched.

Some comments on the F7U-3M can be found here:

A VF-112 F3H-2M with a Sparrow I:

It appears that the operational Sparrow Is were painted black, although the pylon adapters appear to be painted sea blue, the aircraft color scheme that preceded the gray/white one.

Putting a radar in the nose of the Sparrow eliminated all the shortcomings of beam-riding and promised a near sure-kill after launch within its envelope and without any further involvement by the pilot of the interceptor. This was the Sparrow II:
Note that both the aft fins and forward wings have shapes different from the Sparrow I's. The forward wings have also been moved forward, either because of a cg change or to provide more control power for maneuverability. Douglas was promoting the Sparrow II for its F4D and F5D fighters and it was flight tested on the F4D.

The Navy continued to fund Sparrow II development for a while after the cancellation of the F5D. Then the Canadians briefly carried it forward as a weapon for the Avro Arrow program. In the end, incorporating a radar in the Sparrow proved to be a concept ahead of its time, one not fully realized until the Phoenix missile became operational.

The practical solution proved to be semi-active radar homing. This put a radar receiver in the nose of the missile that provided guidance based on the reflection from the target of the radar transmission from the fighter that launched it. This was the Sparrow III, as depicted in its July 1960 Standard Aircraft Characteristics chart (there were many detail changes over time):
The wings and fins were basically the same as those on the Sparrow II although the forward wings had been moved aft to roughly the same location as the Sparrow I's. It was first deployed on the F3H-2 (no suffix and equipped with a different radar than the F3H-2M; for more on the F3H, see

The Sparrow I and III used slightly different launchers. See

The combination of the Demon and Sparrow finally provided the fleet with an effective air-to-air missile defense against jet bombers. The F3H-2 was soon replaced by the F4H Phantom II,which was specifically designed to be a Sparrow-armed fighter.

Wednesday, August 21, 2013

A3D (A-3) Flap to Pylon Fairing

I was having trouble visualizing the A3D wing flap to pylon interface from available pictures so I stopped off at the excellent New England Air Museum at Bradley Field north of Hartford, Connecticut and took a close look at their A3D.

In summary, the aft part of the pylon fairing is attached to the flap and pivots with it when the flap is lowered.

What I indicate to be a rub area might just be dirt and there may not actually be a pivot point between the fairing on the flap and the pylon although it seems likely that there is since there is an access panel there...

This is a Bill Spidle picture of the extended flap, showing how the top and bottom of the forward edge of the fairing on the flap have moved with respect to each other (top going aft and bottom going forward).
Note that the forward edge of the flap itself has moved aft, creating a slot between it and the flap cove.

The inboard side of the fairing is quite different.

In another Spidle photograph, the flat area at the top of the interface is apparent.

And the view from the bottom shows that the split line between the pylon and the flap fairing is perpendicular to the flap hinge line. (This picture is actually the left side flopped but the fairings are mirror imaged.)

Why such a convoluted arrangement? My guess is that it had something to do with the aeroelastic problem that Douglas had with the relatively thin, high aspect ratio wing. If you can get a good look at the pylon, you'll see that it is cambered at its aft end so as to generate lift outboard and below the wing for some important reason, since lift results in drag. (The purpose might be to stiffen the pylon/engine nacelle combination by loading it to one side; it is therefore less likely to "wobble" in roll or yaw.) The pylon is also fairly wide at the aft end of the wing torque box, probably to provide adequate torsional stiffness to the wing. A fairing on the pylon aft of the wing torque box is therefore desirable to reduce drag. If you want as much flap as possible (i.e. not have an inboard section and an outboard section with a gap in between for the pylon fairing), then the fairing has to be attached to the flap and if it's attached to the flap, when it pivots it moves perpendicular to the flap hinge line, not in parallel with the pylon, which means it can't retract within the pylon. And so you wind up with something as convoluted as my hypothesis...

I don't know if the Trumpeter kit reflects this area accurately or not.

Tuesday, August 20, 2013

Grumman WF-2/E-1B Redux

I covered the Grumman WF-2 Tracer configuration fairly well here:

One question was whether the 1/72 Mach 2 E-1B fuselage length was correct. Jackman on ARC (Aircraft Resource Center) has begun a thread (here) on building this kit and in the process, determined that the overall length at least is correct. I'll watch his progress with some interest. Hopefully he won't burn out like I did with the Falcon conversion. See

Things Under Wings - Douglas Low-Drag External Tanks

I've provided illustrations of the various Douglas low-drag external tanks here:

and a survey of 1/72 scale tanks in various kits here:

Freightdog ( is now producing 1/72 150-gallon and 300-gallon (finned and bobtailed) Douglas external tanks as well as the D-704 refueling pod. Colin sent me samples and they look really good, both size and finish. Note the separate and finely molded turbine on the D-704:
(Note that the jettison pipe is on the bottom of the tank.)

Pablo Ziegle called my attention to another 1/72 option for 300-gallon tanks from Attack Squadron in Poland.

Hannants is listing them ( Each set includes three tanks and the fin options for each. Pablo is awaiting a set so he wasn't able to comment on the accuracy or quality.

Sunday, August 18, 2013

Early SH-3 Configuration by Jodie Peeler

Jodie Peeler provided the following information on the configuration of the early SH-3s; note that the Fleet Introduction Program for the SH-3, then designated HSS-2, was accomplished in late summer of 1961 and deliveries to fleet squadrons began to be accomplished immediately thereafter:

While rounding up some references for the Mercury recovery helicopters, I found this picture that's of particular interest to your Tailhook Topics Draft post,, about the Sea King.

It is a screen capture from a film taken aboard USS Intrepid on 24 May 1962; it is HS-3's HSS-2 BuNo 148964 landing aboard Intrepid with astronaut Scott Carpenter inside.

Four interesting things about this HSS-2:

-- Both air data probes over starboard side of cockpit;
-- No rotor cap;
-- No flotation bags on the sponsons; and
-- Take a look behind the transmission hump - there's no little doghouse back there.

In a quick look at my hard drive, here's what I've found, if reviewing the pictures of Gemini recovery helicopters (which were all members of fleet ASW squadrons) can be considered a decent cross-section:

-- By early 1965 some SH-3s had received the doghouse. The Gemini 3 recovery helo (BuNo 148984) had it in March 1965. The Gemini 4 recovery helo (BuNo 148999) didn't have it in June 1965. By the Gemini 5 recovery (August 1965, with BuNo 149005) it shows up and remains consistent. It appears those built without it got the mod whenever they could.

-- The air data probes consistently appear separated by early 1965

-- Flotation bags had come in by early 1965

-- Main rotor caps really don't show up a lot until about the end of 1965*

By December 1965/early 1966 the "standard" SH-3A/early SH-3D configuration has become the norm, with doghouse, separated probes, rotor caps and flotation bags.

The VH-3A/HSS-2Zs were delivered with the rotor caps, but without the doghouse. By June 1963 they had been fitted with the doghouse. Not sure when the air data probe configuration changed; probably sometime in 1964 or early 1965. I don't believe VH-3s have ever carried flotation bags, at least not while on white-top duty.

* In case you want to build your model in this early configuration, here is a photo of the uncapped rotor hub from the 16 January 1961 issue of Aviation Week, page 52.
Good luck with that...