Canted tail rotor pylons, why?

[JohnDixson]

Canted Tail and Boeing vs SA UTTAS Competition

IFMU,

You have a good memory: I do recall that we asserted that the canted tail provided 400 lbs of hover performance ( simply the vertical component of the tail rotor thrust ).

But in fact there were two events during the fly-off that illustrated more than a 400 lb hover performance difference between the two candidate ships:

1. For training the operational Army pilots with sling loads, the Army had made up (7) 55 gallon drums filled with concrete and some odd iron and each weighed 1000 lbs. We trained on the same day as Boeing at Shell Field over toward Enterprise Al. With full fuel ( at first ) we and our student picked up seven cans, took off and did the syllabus. Did that for each student. Boeing then got the cans and started with seven, but couldn't get them off the ground, then tried six, again couldn't get them off the ground, and finally got five off the ground, barely ( I was looking very closely! ).
2. At the end of the operational evaluation at Ft. Campbell, the Army wanted to perform an external lift of an infantry vehicle called a Gamma Goat that the infantry had high hopes for. Weighed 7100 lbs. Two Army pilots picked it up in our machine with a full gas tank, flew it around for pictures and put it back down. The Boeing machine then picked it up and did the same. However, the Boeing crew had done a pretty aggressive strip job, took out all of the interior and troop seats and all but one comm radio, and had only ( we were told by the Army people ) 500 lbs of fuel on board.

Bottom line was that there was a huge difference in hover performance between the two. There was more than just the canted tail involved here though: the Boeing machine had a five foot smaller main rotor diameter (!) and a one foot smaller tail rotor diameter.

As I recall the Boeing production proposal to the Army addressed the hover performance shortfalls with larger rotors, but of course this meant a big redesign, a re-qualification and re-flight test of the whole main and tail rotor and drive train system. SA was good to go as is.
Thanks,
John Dixson