MH-53K Updates?

[JohnDixson]

Eval:

Your point re the final part of an approach is well taken. One of the design decisions for a single rotor machine is what forward shaft tilt to install. More forward tilt and you get a more level fuselage at cruise ( assumimg no controllable horizontal empennage ) thus lower drag/more speed. Also get lower shaft stresses/higher life on the shaft. More nose up in the flare.

In the larger world of single vs tandem, there are two other subjects which have been put out in the media but conflict with the performance of aircraft that are in production. If you'll allow me:

The first is that tandems always have a wider center of gravity range due to their configuration. Some time ago, when we were doing the MH-60K and Boeing the 47E, both for the TF 160th troops, I looked at the 47E CG range and compared it to the 53D. You can do this at your leisure, but in fact, at max weight you'll be surprised at who has a small advantage.

The second is that the tandem has a huge advantage with regard to crosswind landing capability. If one were comparing to single rotor machines designed against the FAA 17 kt criteria, that argument would stand, but that isn't the case nowadays. The last few machines that SA has put out we see a 35 kt crosswind capability in the manual, and in fact the flight loads survey test point data includes 45 kts-both directions. This subject, of course, was a huge discussion point when SA proposed an H-60 version as a replacement for the USN H-46 Vertrep aircraft. We conducted two evaluation flight sessions for senior operational USN aviators at the Stratford plant and that question was put to bed ( I heard that the second session took place because there were some folks who didn't quite accept the report from the first group and had to see for themselves ).

Disclaimer: After flight school graduation in May 1963, I was assigned to the Test Board at Ft Rucker ( service test, not engineering test ) and immediately was checked out in the CH-47A, of which we had three production prototypes. They were fine machines, easy to fly ( certainly, compared to the H-19 C/D aviation school aircraft, they were fantastic! ) and generally a lot of fun, especially for a young pilot right out of school. My instructors were to Boeing test pilots, who were assigned to the test program there. They never tired of answering my often naive questions.

Now, there is a site where you can look up US Army CH-47 aircraft by tail number, and none of these Test Board machines are now D models ( in fact we lost one before I went to Vietnam due to a main blade structural failure ). Reason for mentioning that was your statement re the new F models being mostly late model D's. Correct me here, but I have a recollection that between 1982 and 1994, the Army recycled all the A,B, and C models and made them into 47D models, so late D models might in some cases be " rather late " A models??

Not to worry, Eval, keeping the single vs tandem discussion lively and current is fun. Have you flown both models?

Best,
John