A B-17 with five engines

There was also a B-17 built with four Allison V-1710s.  I have long thought that could be modeled by taking a 1:72 B-17 kit and four P-40 kits :-)  This ship was built to test an alternative if the radials got to be in too short a supply.

There have been quite a few pretty interesting test beds;

Avro Lincoln / R.R. Tyne (Merlin's shut down);

Lancaster with STAL Dovren;

B-58 with J-93;

VC-10 with R.R. RB211;

B-47 with Orenda Iroquois;

Vulcan with Olympus 593 (Concorde);

757 Honeywell test bird;

P&W B720 test bed;

A model I posted some years ago.

It's the T34 "Turbo-Wasp". The single t34 turbo-prop engine is more powerful than the combined horsepower of the four Allison V-1710 radial pistons. The engine went on to be used in the C-133 "Cargomaster".

I remember going to Pratt & Whitney airshows in CT when I was a kid, they had one of those B-17 testbeds on display there.  pretty cool....