sideways flight - mast bumping!!!

[anti-talk]

I think that have read somewhere that sideways flight above 17 kts in an R22 can induce Mast Bumping.

Was I wrong and if not would some of you care to comment, its a manoever that is some times asked on photo - flights setting up the shot but having the wrong perspective.

I am loathe to do it as it also induces TR vortex ring state (prefering to go around and set up again) - perhaps this is what I have read before.

Any contributions would appreciated.

[Gordy]

The 17kts you refer to is in the r-22 manual where it refers words to the effect of "sideways flight has been demonstrated upto 17kts". It mentions nothing about mast bumping. The 17kts is all the manufacturer is required to demonstrate during certification testing. I never had a problem doing what you are suggesting. I will leave the rest for more knowledgeable people to answer.

[slowrotor]

I am no expert on the r22, however I think your answer may be found in an airworthiness directive issued for the r22 that concerns some flight limitations.
Sometimes pilots think A.D.'s are only a concern for mechanics and inspectors.... not true... check the airworthiness directives for the aircraft you fly for updates to the flight limitations if any.

[Gordy]

OK, Have not flown the R-22 in many years, but just checked a manual. I stand somewhat corrected. An addendum to the Normal Procedures section, issued per FAA AD95-26-04 talks about mast bumping among other things.

I quote in part:

"pilots are strongly urged to follow these recomendations:

3)Avoid sideslip during flight. Maintain in-trim flight at all times."

This does still not prohibit sideways flight above 17kts.

[goaround7]

Was it perhaps to do with rapid transition from eg left bank to right bank ?

I was taught with Jet Ranger to pause 'wings level' momentarily mid manoeuvre when doing this, to avoid mast bumping sideways, in a similar way to the normal nose down, reduced g action that causes most mast bumping.

[anti-talk]

yep we are taking ' vertical' or as near to vertical shots as possible which need the aircraft to be sharply banked over for a second or so. and that is what concerns me as there are two methods to do this:
Rapid sideways flight
or fly over the target slightly offset and turn in sharply over it - this works really well for comfort but gives the photographer very little time to react and takes time to set the shot up again.

Clearly an external mount would work better!

[Gordy]

Try doing a shallow bank turn over the subject----the skids on an R-22 ar not that far out.

[fulldownauto]

The R22 will do what you're asking.

I've flown it sideways over freeways for photowork. I would guess I had it up to at least 20 knots. It's difficult and you have fight the helicopter somewhat but it will perform. I never had any indication or thought of a problem with mast bumping while sideways. Be careful though, with a pedal pushed to the floor and the cyclic in an odd position, things can go south quick.

I don't see where the 17 knot figure comes into this. 17 knots is the maximum demonstrated controllability in a hover at high density altitude, not a sideways flight limit recommendation. Though I think the manufacturer can certify this not by waiting for 17 knot winds at high density altitude, but by flying sideways at 17 knots.

There is no 'real' difference flying sideways at 20 knots compared with a hover in a 20 knot crosswind.

[helmet fire]

I feel like the Lone Ranger here......
I have no R22 time, so am probably gobbing off about stuff I dont understand: if so forgive the error,

however....,

is it just me that sees Gordy's post re the AD? The manufacturer seems to be strongly urging pilots to avoid out of trim conditions yet the majority of the rest of you are saying go for it. Perhaps you guys know something the AD author doesn't?

If the R22 is not up to the job, and it quite clearly seems not to be in this case, use a more suitable machine. Secondly, in all the years I have done aerial photography, getting the vertical shot does not require slideslip flight unless some sort of timing issue arises. So, I would suggest either using a more suitable airframe, or taking more time to avoid becomming yet another R22 mast bump accident that we can debate with Lu for pages and pages.

Goaround 7, what you were taught on the Jetranger has no basis in theory. The mast bump you are refering to is G related, not roll rate related.

[anti-talk]

thanks for that - yes it is uncomfortable going sideways to the left rapidly and the aircraft is a handfull but it appars to be the best method of gettting the job done without losing a photographer overboard by asking them to lean too far out!
That is if we have to work with a 22 and as a lowly line pilot - I do as I am told! An articulated system would be a better platform me thinks.

[Quick Release]

Not about mast bumping but Re: side wards flight.

R22.. fast side slip or sidewards flight, it may not be written but maybe the words of the sentence that are missing may be to do with the doors, think of the door on the low pressure side during a slip and the vent opened on the other, and door is only pinned with a single pin!, i have seen a door double up and seen a few with stress cracks, may be something to concider.

[fu 24 950]

The top Shot, must have a top shot, , hear it on most photo job here in Hong Kong. We use a as355n , but it is not the machine ,but the way you do it. I do circles, orbit's and very steep turns. if the man with the photo machine is behind you , all the better,but if as per usual, 1 in the front left, 1 in the back left, it is a bit harder . Go round and round at about 40 kt's, not to fast or hard to make them throw up , but alot of time to get their shot

[NickLappos]

The distinction between out of trim and side flight is an important one.

Side flight is tested and approved, follow the flight manual. It is not "out of trim" and is not dangerous.

Forward flight out of trim is what is the difficulty, where the pilot uses large pedal inputs while in forward flight.

Out of trim is a problem for teetering rotor helos because the horizontal tail and fuselage create fairly large aerodynamic inputs that try to upset the aircraft, so the pilot puts in large cyclic control inputs to keep the aircraft level. These cyclic inputs create large flapping situations, perhaps close to mast bumping. If the pilot is out of trim and also maneuvers the cyclic a bit, it could be even worse.

These tips are for all teetering rotor helos, even Hueys and Jet Rangers. In fact, the sideslipping (out of trim) issue was uncovered during US Army tests of Hueys after a mast bumping accident.

[anti-talk]

As usual thanks Nick, that is the distincion I was looking for - I was aware of out of trim probs but wasnt sure about sideways flight against out of trim.

Tried the tight circling option the other day but photographer was slow with each shot and ended up puking down the side of the aircraft - not surprised as he is focussing on a single spot down while his body is going round in circles.

Will try less steep and at a slower speed and see if that works - Thanks.

[vorticey]

havent done much in the 22, but alot of fiming in the 44 and i find the 44 to fly sidways best around 15 - 30 knots. any less and it gets twitchy with tail rotor votex one way and main rotor interferance on the tail rotor the other way (i think this is why) and any faster and it starts to tip over (too much drag i think). so as long as you keep an eye on how much cyclic your using to hold it steady (sidways speed) i cant see how mast bumping can happen

[hemac]

That is if we have to work with a 22 and as a lowly line pilot - I do as I am told! An articulated system would be a better platform me thinks.

You may well be a lowly line pilot but you are still the pilot in command and as such responsible for the safety of your aircraft and it's passengers.
Getting the job done is obviously important, but at what cost?
I can't offer any information on the technicalities of the this issue because I don't know, I would urge caution if you don't either.

H.