Rigid Head - Sloping Ground

[Rocket Surgeon]

I noticed a thread on "that other helicopter forum" where someone has asked about the technique required to make a sloping ground landing in a Bolkow 105/EC 135/BK 117.

The implication being that for these rigid types, the usual "method" is not appropriate.

Discuss.

[Thomas coupling]

No significant difference, really. Lower the cab until one skid in contact, counter the rotational effect around the skid contact point and feed in 'up slope' cyclic until the rest of the undercarriage makes contact. centralise cyclic on the MMI (mast moment indicator).
This last statement is new to pilots of rigids in that they are getting feedback from the bending of the rotor mast. Comply with FLM limits and the bargraph (135) stays green (ish!) and your safe. The MMI is not relevant while NOT in contact with the ground.
The 105 has an analogue meter I believe, as an MMI.

[Bomber ARIS]

I am led to believe that the Bolkow MMI is of relevance in the hover too, where it is used to check that the C of G is within limits.

[ec135driver]

No one is really going to be interested but here's the answer.

TC is RIGHT! awful thing to have to say but there goes.

The MMI in a Bo105 is a conventional round dial with a single needle sweeping in a clockwise arc from approximately 7 o'clock to approximately 5 o'clock. About 1/3 the way around the sweep is a single black. marked radially relative to the dial. The RFM states that it may be used to check the forward CofG in the hover. The last part of the sweep is coloured yellow to indicate nearing the limit of mast bending and finally a red line. Hitting the red line (or indeed exceeding it - tut tut) will illuminate a red light, co-located on the dial.

So - no special technique, just don't light the light

I must get out more

[NickLappos]

Simple reason why the mast moment can get you introuble while resting oin the earth's surface:

The earth can't be moved, so the moment can be an awsome thing.

While airborne, the high moment makes the aircraft accelerate in pitch or roll, and the pilot stops the maneuver before it gets to very high moments.

[SASless]

But Nick....it is only momentary at best (or worse) is it not?

....and if one is merely "resting" on the surface....would it connote a non-momentary flight condition?

...and if the Earth intervened before the pilot introduced a contra-coup input...would not time appear to stand still to the interested observer?:uhoh:


Returned late to the office after a day in the mountains around St. Helens.....what a gorgeous day! Elk all over the road....a Coyote in the Huey in the pilot's seat this morning. Bit of a surprise that! Customer thought it hilarious....the pilot thought it less than humerous. The Coyote did not offer an opinion.

[John Eacott]

Up to a point, the BK117 sloping ground landings are "normal". The trick is to know when it stops being normal! 8 degrees all round, with 11 degrees when sloping to the left, and 5 degrees if the MMI is U/S, are the book limits, but cyclic trimming to keep the rotor disc level can have an impact well before that.

Above 5-6 degrees, some caution is needed, and at or near the limit, there is a very good chance that the MMI light may flicker. If it goes on and stays on, apart from an inspection, there is a reduction of 100 hours off the remaining life on the MGB bolts.

On extreme slopes, I accept a "collective" landing or take off, with little cyclic input once past about 5 degrees of trim: messy, but a bit of skid wobble is far better (IMO) than pinging the MMI. If the MMI gets into the yellow, and there is still a degree or two of slope left before both skids are on the deck, leave the cyclic trim, just lower the lever and accept a bit of slip from the skids.

[the coyote]

Big night the night before, that's why.....;)

[helmet fire]

John is right - and I am sure he would agree that the collective technique should only be done on smooth ground, and with a smoother hand. Or you could just not fix the MMI and there is no worries at all!!
:) :) :eek:
The most worrisome time in the BK117 with the MMI is during running landings. I am usually more attracted to the frighteneing outside picture, but if you dare to look in you will be quite distracted! Though I do recall hearing from an Aussie that had been taught by the BK test pilot that he had been told by said legend that the two things he wished he hadnt incorporated in the BK were the constant force trim system and the MMI.

Nick, at a certain Ft Eustis school, I was told that the reason we should limit fixed stabilator training (ie stab failure) in the Black Hawk was because it exacerbated mast bending moments, and I subsequently took that knowledge back to the back water from whence I came. A myth, or fair enough?

[SASless]

In the mushy portions of my alcohol ravaged brain....I seem to recall being told the reason the MMI even exists was for use during flight testing of the aircraft and for some reason....MBB left the MMI in the aircraft at time of certification and thus we now have the system to contend with.

[Bomber ARIS]

SASless,

There are engineering checks to be performed if one exceeds an MMI limit, therefore I believe that the MMI gauge was always destined to be in the production aircraft.

This theory is further supported by its appearance in the BK117 and the EC135.


I concur with helmet fire, that it's quite the show if you can ever spare an eyeball to check out the MMI during a running landing. Although these days, if running on in a 135, you'll get the bong if the surface is too rough!

[Oogle]

Slope landings in the BK117 and BO105?? My advice:

SLOWLY, SLOWLY!!!!!

Too many pilots I have endorsed on these aircraft forget this one simple point. If you take it slowly you may be lucky to reach the 11º slope to the left but it can turn messy really quick.:{

BTW, the black line painted on the MMI (BK and BO) indicates the FWD C of G limit. If the needle is below the black line all is good.

[Vfrpilotpb]

Forgive my misunderstanding of some facts, but this BO105 with the bendy transmision shaft, but under this sloping ground landing does it bend up to 8Deg out of true, if so what is the service life of such a shaft, because no one will record the number of times sloping ground is landed on, so there must be a finite amount of input at the original design of this item.

How many other Helis have a similar MR shaft arrangement?


Vfr

[Flying Bull]

Hi there, Slope landings in the BK117 and BO105?? My advice:

SLOWLY, SLOWLY!!!!!

Too many pilots I have endorsed on these aircraft forget this one simple point. If you take it slowly you may be lucky to reach the 11º slope to the left but it can turn messy really quick.:{

BTW, the black line painted on the MMI (BK and BO) indicates the FWD C of G limit. If the needle is below the black line all is good.

Oogle is absolutly right, smooth control is needed - but when you are smooth with the BK you can exceed the sloping limits, without exceeding the limit on the MMI.

I had 15° nose up with the front skids on the ground - MMI still in the green - and you can get the MMI-light flickering - when taking off from a flat surface - when the stick isn't centered properly.

And yes - I know, it isn't allowed to exceed the limits - it was a demonstrationflight - and in this case the limiting factor was the stress on the rotormast and not the slope
http://www.pprune.org/forums/images/smilies/rolleyes.gif.
You can also exceed the MMI-limit recovering from a dive - with a high power setting - important to know, when playing with the helicopter.
Better to reduce the collective, before pullong out and appling it then again - less stress for the mast and no lights ;-)
A little helpful trick with the BK 117 is, to depress the FTR-button shortly when in hover, so that the BK would hover on its own. After landing and reducing power, the MMI will then be nearly perfectly placed - as well as the stick for the next takeoff.

Greetings "Flying Bull"