Project "Seahorse"

There is also some confusion I believe over the name of the aircraft. Some resources call the Naval-modified P-51D an “ETF-51D”, but this isn’t correct. The aircraft never had a change of name while it was in the hands of the Navy (not even a BuNo assigned to it), and if it had, it wouldn’t have been in that form, for a North American product in U.S. Navy hands would have had a “J” in the title. The term “ETF-51D” came later, in the post-war years, with the NACA operated F-51D’s. “ET” was added to the front of the title, meaning “Extended Tail”, as NACA added taller tail fin caps to their F-51D’s (which Cavalier later copied and used in their Mustang conversions).

There is the possibility that this particular airframe, 44-14017, was handed over to the NACA after the carrier trials, and later became an “ETF-51D” in the hands of the NACA. There is a photo of the ETF-51D “NACA 102” which appears to show the same rudder and lower tail-cone modifications as seen on 44-14017 during the carrier trials (note the Bell X-1 style model airframe profile mounted to the wing). Photo comes from the NASA archives: http://i7.photobucket.com/albums/y282/Bomber_12th/GPN-2000-001252.jpg

I know this isn’t the flight simulation section of the forum, but a very accurate depiction of this modified P-51D-5-NA was produced for Microsoft Flight Simulator ‘X’, using all of the knowledge/facts available about the modifications to the original. Here are some screen captures which illustrate some of the modifications as already described. The aircraft had certain early details, like the white recognition light on the spine, the early dorsal fin fillet, fabric elevators, but a late D-5 into D-10 production style canopy (not the higher profile example as seen fitted to most P-51D-5-NA’s).

Interestingly, the FAA had no issues with inlines – Fulmar, Firefly Seafire etc…

I would say that with the utter garbage that the Fleet Air Arm procured as front-line combat aircraft in the period, never mind ‘fighters’, that the difference in reliability / vulnerability of in-line versus radial engines was of little consequence!

During a missed approach or a wave-off, power has to be re-applied gently.

To be fair – that applies to any powerful prop aircraft and quite a few inexperienced pilots were caught out by torque rolls !

rgds baz

The article fails to mention the other reasons for the Seahorse project to be dropped.

http://mustang.gaetanmarie.com/articles/naval/naval.htm
In the words of the test pilot Lt. Elder, who made nearly 150 simulated launches and landings with the ETF-51D and the actual shipboard arrested landings and take-offs, “from the start, it was obvious to everyone that the margin between the stall speed of the aircraft (82 mph) and the speed imposed by the arrester gear (90 mph) was very limited.”

Bob Elder “made all carrier landings at the speed of 85 mph. Luckily, the Mustang reacted well, even in the most delicate situations. One just had to use the throttle wisely.” Elder reported that speed control on the ETF-51D was excellent. He also stated that “the forward visibility was good and never gave me any problems. In fact, fighters with radial engines such as the F4U or F6F were worse than the P-51 in that respect.” The aircraft also behaved well during catapult launches.

But everything was not perfect. As previously mentioned, the margin between stall speed and maximum engagement speed was small, too small for safety. Rudder control at low speeds and high angles of attack was inadequate. In addition, landing attitude had to be carefully controlled to avoid damaging the airframe upon landing.

One of the handling quirks of the Mustang was also potentially dangerous. During a missed approach or a wave-off, power has to be re-applied gently. If not, the aircraft could roll rapidly, or even snap-roll. At such low speed and altitude, the result could only be fatal.

The carrier suitability trials were rather short: only 25 landings and launches were made. Elder wrote “Although I had “premiered” many US Navy aircraft carrier landings, no such experience had been as interesting as with the Mustang”. Nevertheless, he did not think the Mustang had its place in naval operations.

Add to that the abundance of the F6F Hellcat and the F4U Corsair, and the impending introduction of the F8F Bearcat & F7F Tigercat, and there just wasn’t a need for the Mustang on carriers.

But NAA persisted:

However, North American Aviation did not forget about the ETF-51D experiments. It later presented another navalized Mustang project to the Navy. This project, NAA-133, was based on the P-51H, the last Mustang model to see production.

Modifications were similar to those carried out on the ETF-51D. The airframe of the NAA-133 would have been strengthened. This was particularly important as the P-51H airframe was lighter but not as sturdy as that of the P-51D. It also included a folding wing design. Two external drop tanks would have been fitted on the wingtips. The rear part of the fuselage was more heavily modified to accommodate the tailhook: the tailwheel doors were lengthened to fit the entire tailhook. The lower part of the rudder was cut out, to make space for the tailhook when in retracted position. Also, the twin dorsal antennas of the standard P-51H were replaced by a single antenna.

The NAA-133 project never went further than the design stage. However, the US Navy did continue to play with the idea of navalized Mustangs for some time. In August 1945, P-51H-5-NA #44-64420 was transferred from the Army Air Forces to the Navy. It was used to determine whether the P-51H had low-speed performance that would allow it to operate from carriers. The handling of the aircraft at approach speeds was considered adequate and much better than that of the P-51D. Once this had been ascertained, no further testing was undertaken for some time.

In late 1947, another P-51H was borrowed by the US Navy: P-51H-10-NA #44-64700. This aircraft was modified by the Naval Aircraft Factory and received a center-line catapult attachment point. The aircraft was used to test new catapult equipment. A few catapult launches were made at different weights, and the type was considered suitable for catapulting with no further modification.

Obviously, the Navy was interested in the Mustang’s long range at a time when early jets had very short “legs” and could not stay over the battlefield or stand patrol for extended periods. Nonetheless, navalized versions of the P-51H appear not to have been attractive enough to warrant further interest. Attempts to navalize the Mustang thus came to an end and the “Seahorse” became an amusing and little-known “what-if” part of aviation history.

In light of the concerns over a hard landing damaging the P-51D’s airframe, the lighter airframe of the P-51H would be even more fragile, despite its better low-speed characteristics.

Of course, by 1947 the early AD-1 Skyraider was about to enter service – with a long range and a massive payload.

The link below shows some photos this unusual Mustang version:

http://aviacaoemfloripa.blogspot.com.br/2011/02/um-p-51-mustang-navalizado.html

The link might give the impression that there were mass trials of the type, whereas the last four images actually show (I think) Mustangs being transported on board a carrier.

I’m not saying it’s ‘wrong‘ to see images of a Mustang on deck, but it just doesn’t seem ‘right‘…;o)

Didn’t the US Navy prefer radial engines over inlines for their better damage tollerance – and lack of cooling liquids ??

Adopting a seagoing P-51 would have meant a change in logistics to cater for the Merlin.

Interestingly, the FAA had no issues with inlines – Fulmar, Firefly Seafire etc….

Ken

Interesting concept, if nothing else the wide track undercart would certainly help the P-51 as a carrier based fighter.

Thanks for posting the pics.

Rob