Kyleb wrote:
sandiego89 wrote:
Large turboprops often sound attractive, but they do have downsides,
With absolutely no knowledge on the subject, I always assumed the problems with the C-133's turboprops were simply the development cycle. Not enough engines in service to work out all the bugs, and since there was no next step engine in the works, the development cycle simply stopped, leaving problems unsolved.
There was likely "no next step" because the turbo-fans coming into fruition at the time were MUCH better suited to large strategic lift aircraft (and some bombers and large airliners). The Turbo-prop was a hoped for compromise with turbine power, but propeller efficiency. It works well is some applications, but can not be scaled up across the entire spectrum as well. Turbojets had the power, but not the efficiency (range) for strategic lift. Others have mentioned the challenges of blade speed and size, gearboxes, etc. Just like the large piston engines were maxed out for large US bombers and transport aircraft such as ever increasing HP versions of the piston 4360 on the B-36, B-50, (K)C-97 and C-124, the large turboprops were similarly maxed out. The C-133 was underpowered for its size and weight even with 4 massive turbo-props. The turbofans on the C-141 (low bypass) and C-5 (high bypass) were much more suited for moving large amounts of air on strategic air-lifters. The turboprop was very well suited for TACTICAL airlift such as the C-130.
JohnB wrote:
Kyleb.
A brief look at the C-133 losses show engines were not the primary caused of accidents. If course that is not to say they didn't have issues and "routine" failures.
One loss over water (thus no substantial wreckage) is theorized to have been an engine issue.
The other nine losses were: Airframe fatigue, fire on the ramp,
prop electrical issue causing a ditching, icing leading to a stall,
two stall accidents at low altitude, and two other over water losses which they think may have been from power on stalls at heavy weights. Finally, a suspected case spatial disorientation.
Data from :Remembering an Unsung Giant, The Douglas C-133 Cargomaster and its people by Cal Taylor, Firstfleet Publishers, 2005. Page 321.
Excellent book.
Other parts of that book highlight the numerous and largely unsolved propellor problems with the C-133. The governor/blade pitch mechanism had numerous problems and was quite complicated. Harnessing and controlling that much torque was especially difficult with the electrically controlled gears. C-133's were often down with engine/propeller issues.
Some of those losses, such as the stalls, may indicate a generally underpowered aircraft (with the noted poor stall warning of the type). The fatigue losses (suspected and known) may be partially attributable to maxed out turbo-props fatiguing the airframe prematurely.
I have had the pleasure of being all over the last C -133 made at the excellent Dover museum, and the docent was quick to point out the large fuel dump lever on the flight engineers panel, stating that an engine loss on takeoff was extremely critical, and the engineer would have been dumping as fast as they could.
Login
Register
FAQ
Search
