Stearman XOSS-1 Competitor to XOS2U-1 Kingfisher

The Stearman Model 85 (XOSS-1) was entered in the competition to replace the Curtiss SOC in the scout/observation role for the US Navy.
The aircraft competed with the Vought XOS2U-1 Kingfisher for the contract. The XOSS-1 a biplane configuration was not able to match the
performance of the Vought monoplane and lost the competition. The aircraft was utilized by the US Navy until July 1941 when it was surveyed
at NAS Jacksonville.
FWIW Surveyed according to COMNAVAIRFORINST 4790.2B CH-1 "5.1.3.14.1 Definition. A survey is the procedure required when Navy property
and DLA material, including IMRL equipment/SE, in Navy custody is lost, damaged, or destroyed"
A recent visit to NARA II afforded the opportunity to scan a few photographs of the XOSS-1 for your reference and viewing pleasure.

Stunning set of photos, thanks a lot for these!

Here's a few more photos from my HD. Apparently the landplane configuration was changed to a sturdier-looking and much more conventional landing gear.

Skyblazer said:

Stunning set of photos, thanks a lot for these!

Here's a few more photos from my HD. Apparently the landplane configuration was changed to a sturdier-looking and much more conventional landing gear.

Click to expand...

The landing gear configuration is different in my two shots and then aerodynamic fairings make it look sturdier!

The upper wing -- are those Youngman flaps or just full-span external airfoil ailerons? In either case, I don't understand their use: conventional wisdom is that flaps are not as effective on biplanes as on monoplanes, and that full-span flaps cause a lot of adverse yaw.

Thank you for sharing the scans of this aircraft!
Very nice-looking apparatus - although not as advanced, like a successor.

Bill S said:

A recent visit to NARA II afforded the opportunity to scan a few photographs of the XOSS-1 for your reference and viewing pleasure.

Click to expand...

By the way, is it first Stearman attempt to enter Navy competition?
Looks, like previously only military types, build by company were Primary Trainers?

Silencer1 said:

Looks, like previously only military types, build by company were Primary Trainers?

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Correct. And only for the U.S. Army Air Corps. (PT-9 and PT-13)

Than you, Skyblazer!

Skyblazer said:

Correct. And only for the U.S. Army Air Corps. (PT-9 and PT-13)

Click to expand...

At least, the company tries to evolve in the other areas - besides the XOSS they also made prototypes of training monoplanes, as well as "X-100" attack aircraft, which impress me, despite many its' shortcomings.


I wish you to find much more interesting stuff during archive' searches!

swampyankee said:

The upper wing -- are those Youngman flaps or just full-span external airfoil ailerons? In either case, I don't understand their use: conventional wisdom is that flaps are not as effective on biplanes as on monoplanes, and that full-span flaps cause a lot of adverse yaw.

Click to expand...

Could you explain this statement?
There were no too much biplanes IIRC, with mechanized wings - however, the newest example of it is now in the air:
http://www.secretprojects.co.uk/forum/index.php/topic,24999.0.html - each of this extensively modified Antonov' wing has been equipped with a large flaps.

Silencer1 said:

swampyankee said:

The upper wing -- are those Youngman flaps or just full-span external airfoil ailerons? In either case, I don't understand their use: conventional wisdom is that flaps are not as effective on biplanes as on monoplanes, and that full-span flaps cause a lot of adverse yaw.

Click to expand...

Could you explain this statement?
There were no too much biplanes IIRC, with mechanized wings - however, the newest example of it is now in the air:
http://www.secretprojects.co.uk/forum/index.php/topic,24999.0.html - each of this extensively modified Antonov' wing has been equipped with a large flaps.

Click to expand...

Look at the trailing edge of the upper wing. It appears that there is a full-span device slightly below the upper wing, with slot between it and the pressure (lower) side of the main airfoil. Youngman flaps were used on the Fairey Firefly; they would look like that in some configurations. Looking at the picture again and looking at some other aircraft, it seems that the upper wing is likely to have external airfoil ailerons, similar to those used on the Ju52 (as an aside, they were not the best design in icing conditions)

Flaps weren't used that much, at least for lift enhancement, on biplanes as they were generally less effective than they were on monoplanes. Usually, however, biplanes would only have ailerons on one wing, and putting them on the upper wing has the benefit of keeping them farther away from spray (in a floatplane) or dirt (on a landplane). Full-span ailerons tend to be avoided because they cause excess adverse yaw, and the root portion of the aileron is not going to be very effective in producing a rolling moment (moment is force times distance)

There was a feature on the XOSS-1 in Skyways #35 from July 1995. A dozen or so pages of text, photos and cockpits layouts.

They look more like Junkers style flaps and ailerons which are more effective in slow airplanes with turbulent boundary layers.

Few biplanes need flaps because they have light wing-loadings - for operations on short, grass airstrips. Since the wings are already large enough for short takeoffs and landings, there is little benefit to adding landing flaps.

riggerrob said:

They look more like Junkers style flaps and ailerons ...

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Agreed in the sense that they are plain slotted flaps à la Junkers practice. But, on the XOSS-1, those upper wing surfaces are full-length flaps - not divided into flap and aileron sections as per Junkers. The Stearman has its ailerons on the lower wings. (Now I'm wondering if those ailerons were also arranged to droop?)