Engineering Division GL- series (1920s aerial target gliders)

[Jos Heyman]

I picked the enclosed picture up from http://www.edwards.af.mil/photos/mediagallery.asp?galleryID=530&?id=-1&page=1&count=48.
It shows the G-3 aerial target glider that, as I can determine, was tested in the late 1920s or early 1930s.
The target was to be used for aerial gunnery training in which a pilot carried his target glider aloft. After release, the glider took several minutes to reach the ground. During this time, the pilot could make several gunnery passes against it. Tests were performed with Curtiss XA-4 27-244 also XP-500.

The factsheet at http://www.nationalmuseum.af.mil/factsheets/factsheet.asp?id=7663 states that the McCook Field Engineering Section developed a series of target gliders in the 1920s, including the G-3. In December 1922 J.A. Roche designed the first model, the GL-1, as a target for anti-aircraft gunners of the U.S. Army Coast Artillery. These early targets were the first and only gliders (manned or unmanned) used by the U.S. Army Air Service.

From my own data: The GL-1 was an unmanned target glider built by the Engineering Division and had serial 23-001 (in a sepaarte series for gliders) whilst the GL-2 (which carried serial 23-002) was a manned glider.

Can anybody provide some more details of this series of gliders? I would love to know if here were any designs beyond G-4 and how many G-3 were built an tested. What time frame were the tests performed? What serials (if any) did the G-3s carry?

I know, this is all specialist stuff, but some of you guys have incredible archives....

 

[Apophenia]

Jos: a little bit more on the GL-1 and GL-2. I'm puzzled by the "G-3" designation.

An image of the GL-1 accompanies "Small Glider Target for Anti-Aircraft Guns", Popular Science Aug 1923, pg 35. The GL-1 is shown on a similar above-wing mounting (but on a DH-4). McCook Field's GL-1 is described as "made of linen, wood, and a piece of metal [the fuselage's 2D tubular structure], has a twelve-foot wing spread." Setting horizontal tail and rudder determined flight path. Descent from 10,000 ft took about half an hour. Other than being mid-winged, the GL-1 looks very much like the later G-3.

J.A. Roche's GL-2 was another high-winged design (recycling the upper wing panels of a JN-4). Jean Roche (longtime liaison between the Air Force and NACA, Langley) went on to develop the GL-2 design into Aeronca's powered C-1 (albeit now with Clark Y airfoil). So, it's not a huge stretch to relate the GL-2 to Aeronca's later TG-5 training glider.

Popular Science Feb 1926, pp 11/12 also discusses aerial targets, showing both towed targets and an air-launched glider. And that brings up the designation puzzle.

All refs mention "G-3" and that's how the restored aircraft is marked. This photo shows 'GL-3' on the fuselage side (along with a large roundel/bulls-eye). Note too that "GL-3" has a fully-covered (fabric?) nose.

 

[Apophenia]

I forgot the image of the GL-2. Photo is from the National Soaring Museum, reproduced in J.N. Grim's "To Fly the Gentle Giants: The Training of U.S. WW II Glider Pilots", AuthorHouse, 2009, ISBN-13: 9781438904849 ISBN-10: 1438904843

 

[Jos Heyman]

This seems to confirm to me that the G-3 designation is most likely some invention of whoever wrote the USAF Museum factsheet and 'interpreted' it as G-3. I think I am going to stick with GL-3.

 

[thanos.massias]

This looks related to the GL gliders.
Notice the "passengers" painted on the side.

https://gallica.bnf.fr/ark:/12148/btv1b9028077w

 

[Stargazer]

This looks related to the GL gliders.
Notice the "passengers" painted on the side.
https://gallica.bnf.fr/ark:/12148/btv1b9028077w

I agree that it is very reminiscent of GL-1 / GL-3 type gliders.
This one, however, looks pretty well tethered to the plane and not liable to be released.
In those early days, there were no wind tunnels, so sticking a model on top of a biplane was the only way to approximate the behavior of a design in the air, however crude.

 

[Dynoman]

Unlike GL-1 with a rounded forward fuselage section, it's fuselage is similar to the G-3's triangular design. However, unlike the G-3's high wing and G-1's mid-wing placement, the unknown glider has a low wing position. In 1922-1924 McCook Field built 13 gliders for target practice. I would assume that this unknown glider is one of the other 10 gliders that flew during this period. (Development and Procurement of Gliders in the Army Air Forces, pg. 3)

 

[Dynoman]

Film of another target glider. Note the different delta planform of the horizontal stabilizer. Film shows crew installing and then launching the aerial target glider.

https://www.pond5.com/stock-footage/item/170560033-1918-experimental-glider-developed-us-army-air-corps-launche

 

[thanos.massias]

A better copy of that footage can be found here:

https://catalog.archives.gov/id/24636?objectPage=2

Stills:

 

[Dynoman]

From an Air Corps newsletter, these GL target gliders had wing structures made from wood with a frame fuselage covered in fabric. The target gliders were often reused. However, continued impacts with the ground would 'loosen' the wing structure to the point that the wings were often replaced (consideration was given to make the wings from metal). I would assume that the wing replacements allowed the McCook Field engineers the opportunity to experiment with different wing placements and tail surface configurations. Since the gliders were uncontrolled, the control surfaces were prepositioned with tabs to allow the gliders to maneuver.
To support naval anti-aircraft gun firing training the gliders were equipped with kapok (cotton derived from the kapok tree) to enable the glider to float. These gliders would fly up to 50 training missions before being replaced.

https://media.defense.gov/2011/Apr/22/2001330128/-1/-1/0/AFD-110422-031.pdf

 

[Stargazer]

chrome-extension://efaidnbmnnnibpcajpcglclefindmkaj/https://media.defense.gov/2011/Apr/22/2001330128/-1/-1/0/AFD-110422-031.pdf

You want to remove the first part of that URL before 'https'...