Merlin Question

[Razor61]

Having just watched the Merlins for two days transiting back and forth from Culdrose to Yeovilton for the practice flypast and of course seeing both the HC3 and HM1 elsewhere i have noticed that no matter what speed they are cruising at, the Merlins are consistently in a nose down attitude.

I know helicopters pitch the nose down to gain forward speed along with the rotors pitching in the same direction but then most helicopters then regain level attitude.

The Merlins however keep this nose down attitude throughout the whole of their transit no matter what cruising speed they select.

What is the reason for this?

[Ivan Rogov]

Not sure about the Merlin but ISTR that early development S-92s had an unlevel cabin during flight, it was solved by lengthening the fuselage.

[green granite]

It's to compensate for the laid back attitude of the pilots. :cool:

[greenhaven]

It's not as nose down as you'd think, unless you're accelerating hard or shifting in the cruise (>135 knots). The radome cover under the nose gives it a slightly nose-heavy appearance from the outside when it's flying.

Interstingly, it's quite nose up in the hover - so may be connected with the fact the fuselage is 22 metres long and is a fairly large pendulum!

Greenhaven

[Winch-control]

The CH47 is also nose down in forward flight... anything less and it would be in a hover....or moving rearwards! I think something like 3 to 6 degrees...is the norm.

[Logistics Loader]

IIRC,

The Tristar flies permanently at 3deg nose up..
Hence why the seats will never be turned round to face rearwards like the VC10.

[nice castle]

CH47's have LCTs (Longitudinal Cyclic Trim), which motor the fixed swashplates in such a way as to make the discs tilt, instead of the fuselage. They run out of authority at about 120kts, so the 3-6 deg nose down would only come into effect from speeds >120 kts up to Vne, 160 kts.

Below 120 kts CH47s have a level fuselage attitude in forward flight.

I'll avoid answering Merlin stuff though.

[Occasional Aviator]

I think it's just more noticeable on Merlin because of the 'long lever' - having the disk in the middle of the fuselage rather than close to the front as on most other types. This means you're able to get into a landing site not that much bigger than a Sea King's, with a cabin not much smaller than a Chinook's.

For the same reason, on long transits in the Merlin, it is worth transferring fuel around the tanks to keep as level attitude as possible - it gets you an extra couple of knots and therefore extends your range.