Skycraft (Robertson) STOL aircraft

[Stargazer]

The Robertson STOL aircraft presented in 1962 introduced a new type of control system especially designed for very low speed flight and patented by Skycraft, Inc. of Fort Worth, Texas, headed by James Robertson. The aircraft was built by Skycraft as a first step towards commercial development, and the U. S. Army awarded the company a small contract to provide flight test data on their control system, with test pilot Paul Eddy* at the controls.

The main idea behind the nose-mounted controls was to keep them in the direct slipstream and increase their effectiveness at low flying speeds. The aircraft could stay under control in level flight at 20 mph, though control effectiveness actually proved better at 40 mph. Main modifications planned for the commercial version included retractable gear and the use of a 12 per cent (chord thickness) wing in place of the prototype's 15 per cent wing.


* Paul Eddy was the Chief Pilot of W. H. DuPont Airways in Miami, Florida.



Specifications

Powerplant: modified Lycoming with water injection, rated at about 420 hp
Normal gross weight: 4,200 lb.
Maximum weight: @5,000 lb.

Performance

Stopping distance: @25 ft.
Minimum take-off roll: 65 ft.
Total distance to a 50 ft. altitude: below 400 ft.



Source: FLYING, May 1962

 

[Bill Walker]

I seem to recall that some of the features of this aircraft, including the canards, showed up later as retrofit kits for some of the Cessna single engine aircraft. Or am I confusing this with another US product?

 

[ksimmelink]

I seem to recall that some of the features of this aircraft, including the canards, showed up later as retrofit kits for some of the Cessna single engine aircraft. Or am I confusing this with another US product?

Roberson made conversion kits for many aircraft (I am more familiar with the Cessna aircraft conversions) to improve takeoff, landing, and slow speed performance.
I know my Dad flew Cessna 185s and 206s with the Roberson STOL conversion which consisted of a leading edge "cuff", drooping ailerons when the flaps were extended, and wing fences to help direct the airflow over the wing.
He also fles a Cessna 172 with Roberson's Wren conversion which added the canard to the forward fuselage and multiple wing fences (see attached picture which is similar to the one he flew). None of these conversions were as extensive as the first post, but they did a great job of increasing performance at slow speeds.

 

[Stargazer]

I always figured the Robertson mod was a different one from the Wren mod, but looking at both there seems to be quite a lot in common.

Here is the Wren 460 modification:

 

[famvburg]

I've never seen or heard of a 172 with the Wren mod and all of the posted pics show 182s. Do you have a pic of the Wren 172?

 

[Stargazer]

I've never seen or heard of a 172 with the Wren mod and all of the posted pics show 182s. Do you have a pic of the Wren 172?

I don't think there was a 172 with the Wren mod, only the 182.

Also, a highly modified 1969 version was known as the Wren 460QB (for Quiet Bird) and is believed to have occupied briefly the DoD's O-4 slot as the before its cancellation (strangely, it has been mentioned as the ZO-4A, the prefix of which is used for "obsolete" types, which could indicate that the type was briefly tested under the O-4A designation).

 

[famvburg]

So ksimmelink made a typo and meant to type '182'?

 

[ksimmelink]

I always figured the Robertson mod was a different one from the Wren mod, but looking at both there seems to be quite a lot in common.

I believe that the Wren mod was made by Robertson. It was just different from their standard mod because it added the forward canard and multiple wing fences, thus it was given different name (even though the standard conversion didn't have a name, just went by Robertson or Robertson STOL, usually was applied to the vertical tail, white lettering on a black stripe)

 

[ksimmelink]

So ksimmelink made a typo and meant to type '182'?

Yeah it looks like my fat fingers or slow brain didn't communicate correctly!

 

[Stargazer]

A photo found on Flickr:

 

[Stargazer]

Previously unheard of projects by Robertson's Wren Aircraft Corp.:

• "Engineering is completed and only production and flight test is necessary to certification of a WREN460C model utilizing a Cessna 180 airframe, thus making available a WREN on skis, floats, amphibious floats, or with conventional landing gear. This version will utilize wings fully interchangeable with the present WREN 460 except that it appears likely that a changeover from the manually operated 180 flaps to electric flaps will be advisable."

• "A kit that can be applied to new and used Cessna 180, 182, and 185 aircraft (and, with slight variations, to Cessna 172, 175, and 206 aircraft) is under development and scheduled for FAA certification and ready for production in 45 days. This kit will give semi-STOL capabilities to these airplanes. Unlike any other such "kits" on the market, the Wren "kit" (tentatively named the Pea Patcher) will have control augmentation for improved safety at lower speeds."

• "Arrangements have been tentatively agreed to with Cessna Airplane Co. to provide engineering data upon which certification can be readily achieved of a full WREN version of the Cessna 337 Super Skymaster (military O-2). (...) The Air Force is quite interested in this airplane, and at least three commercial sales are already assured. To be designated the TWIN WREN 840, this should be beyond question the world's safest airplane. It should prove of interest to air taxi operators, especially those offering short-haul, scheduled operations in the New York area." (1)

• "A future WREN entirely of company design and manufacture is in the preliminary design stage and basic wind tunnel tests have been conducted. This design utilizes a lifting-body principle. In its initial phase, it will utilize exactly the same wings as presently used on the WREN 460 to save time and money. This first model will be an eight place aircraft capable of cruising speeds near 200 mph yet retaining the present WREN 460 slow speed capabilities. This airplane will have many advantages for scheduled air taxi and bush airline operation. It will have practically no center-of-gravity (CG) loading problems. It's retractable landing gear can be heavy duty with large, high-floatation tires. It will be very simple and inexpensive to build. Its flying characteristics will place minimal demands on the pilot. It can be quickly convertible from passenger to cargo with ample room for on-board storage of passenger seats. It will be readily subject to growth potential to larger versions."

Source: The Wren 460 Story, Wren Aircraft Corp. company brochure, 29 Jan 1968.



(1) (not in brochure): Famous aircraft designer Al Mooney apparently worked as a consultant in 1968 on the Wren/O-2A program.

NOTE: Bold type is mine.

 

[Jos Heyman]

Here is my contribution to this topic:
DOD Directive 4120.15-L (April 1974) identifies the ZO-4A designation which was used for a project to develop a quiet aircraft. Funding was cancelled in Fiscal Year 1970 (AWST, 8 Dec 1969, p.26).

Although there is no evidence to support this, it may be possible that this designation was used for a 1969 USAF proposal to purchase 28 Wren 460QB aircraft in lieu of the Lockheed YO-3B. The 460QB was a modified version of the Wren 460B, itself a derivative of the Cessna 182. The basic Wren 460 had a span of 36’2”, 11.02 m, a length of 27’4”, 8.33 m, a Continental O-470-R and a max.speed of 160 mph, 257 km/h. The designation OX-1 was also associated with this.

 

[QAVet]

Here is my contribution to this topic:
DOD Directive 4120.15-L (April 1974) identifies the ZO-4A designation which was used for a project to develop a quiet aircraft. Funding was cancelled in Fiscal Year 1970 (AWST, 8 Dec 1969, p.26).

Although there is no evidence to support this, it may be possible that this designation was used for a 1969 USAF proposal to purchase 28 Wren 460QB aircraft in lieu of the Lockheed YO-3B. The 460QB was a modified version of the Wren 460B, itself a derivative of the Cessna 182. The basic Wren 460 had a span of 36’2”, 11.02 m, a length of 27’4”, 8.33 m, a Continental O-470-R and a max.speed of 160 mph, 257 km/h. The designation OX-1 was also associated with this.

Jos,
The USAF acquired (11 to 28) Tail #s, and converted 460s to 460QB (for Quiet Bird) in, currently, the Vintage Flying Museum (VFM) at Meacham Field in Ft. Worth, TX. They were planned competition to the YO-3As. The program failed ca 1969. A covert program, we're only now learning some truths - See VFM, DRS