North American T-28 / Volpar AT-28F


Senior Member
26 May 2006
Reaction score

the North American NA.284/BT-28 was converted into twin engined
strike and close-support aircraft by Volpar,and given an unofficial
designation,A-28F,but it remained only a project.
I'm surprised this isn't already mentioned here other than in passing comments. Anyway, I found this photo copy in one of my folders and don't know where I got it so I can't credit it to anyone. It may be a copy out of one of several books I have. I can't locate a couple of books I have on the T-28 at the moment (in storage) and my first sighting of the AT-28F was in a book from the late '70s / early '80s, IIRC, called "Closet Cases", again IIRC. Anyway, it was a proposal by Volpar to install 2 Garrett TPE-331s of some sort and a large nose cone in place of the radial engine. I've not seen a lot of info on the proposal.


  • IMG.jpg
    136.5 KB · Views: 622
famvburg said:
I'm surprised this isn't already mentioned here other than in passing comments. ...

Topics merged ;) and as an add-on two drawings from Squadron Signal N° 89, which mentions
the Volpar AT-28F, too. The piston engine was replaced with two Garrett TPE 331-3U turboprops
of 904 hp each, using so-called "Package Power Conversions" off-the-shelf propulsion units.
The nose section, repacing the piston engine was detachable and easy and quick exchangeable.
Noses with four .50 caliber guns, ECM equipment or for photo recce were designed.
Additionally the AT-28F had six underwing hardpoints for up to 4,000 lbs.
Claimed performance were a top speed was 330 mph, service ceiling of 28,000 ft and a range
of 1,540 miles (2,800 with aux tanks of 165 gallons each).


  • Volpar_A-28F_01.gif
    110.7 KB · Views: 618
  • Volpar_A-28F_02.gif
    42.7 KB · Views: 598
Is its designation A-28F or AT-28F? All I have ever seen is the AT-28F designation. Of course, officially, AT would have been correct.
I would support AT-28F. Having said that, we have to understand that this is not an official USAF designation but rather a private one.
The "A-28F" designation (as written in my post) was just an error during scanning those pages, sorry. :-[
Jemiba said:
The "A-28F" designation (as written in my post) was just an error during scanning those pages, sorry. :-[

It's not. It actually appears in one of the scans (from a Squadron Signal book, I believe).

It may not have been official, but it was in line with the AT-37D Dragonfly becoming the out-of-sequence A-37...
Ah, you're right, sorry, maybe that was, what led me to using those file names.
The article actually speaks of the "A-28F" only.
It would be an unofficial designator in any event. Quite apart from the idea of strapping two engines on a wing that was never intended to take them, and introducing 1800 shp and asymmetry to a 1400 hp single...
The engines are said to have been mounted at the position of the landing gear, so at least at a stronger
point of the wing.The general idea of converting a single engined design into a twin engined one, seems
to have been en vogue, the same was proposed for the Breguet Alizé
BTW, I still haven't found a timeframe for the A/AT-28F, not in the Squad Sig, article and not in this
Probably no worse than strapping 2445 horses to the airframe, as in the YAT-28E.
There have been several real-world single engine-to twin-engine conversions. How much redesign of the wings were involved I don't know, but I'm sure there would have been some local strengthening to the T-28's. Among real-world conversions that I know of right off were the Twin Navion, Twin Mooney and a Twin V, conversion to the Beech V-tail Bonanza. Not sure how much factory built single vs. twin engine types such as Piper and Beech have built over the years could be considered conversions or not, but it isn't that unusual.
Top Bottom