A109 nose wheel
 

Hi

If someone of You knows the answer , appreciated .
Is it any danger when NOSE WHEEL LOCK is OFF during landing gear retraction that nose wheel can be moved up when turned and destroy the bay ?
Couldn't find anything on that in PM , QRH says only that must be ON during before TO and landing but actually wondering why .

Regards

Nosewheel lock
 

Don't know about 109, but read up on nosewheel shimmy, that's why it's supposed to be locked:rolleyes:

Normally when a nosewheel extends when the weight comes off it is straightened by a cam arrangement on the oleo. Some helicopters have a manual lock as well. Should the nosewheel not extend depending on type it can still fit it the nosewheel bay. However, if it is twisted off centre on lifting then it can go in sideways.

It then depends on the nosewheel design as to whether it can go in sideways or not; if it can one wheel or axle will normally thump the roof.

Hi, I speak only regarding 109 as the only heli with wheels I have on my types, I wouldn't be too afraid about the wheel being turned wile u retract the landing gear, as mention above, when u lift off the shock will extend and automatically turn the wheel straight due to a shaped mechanism that any time the shock fully extend ( means no weight so u in the air ) will move the wheel straight.
As far as my experience it's more important on landing to have the wheel lock, once u lower the collective it helps a lot to keep the heli steady and not jerking left right wile u apply pedals.
Ohh by the way, whatch out gps speed coze shimming its a pain in the a.. if u take a taxiway light at more then 20 kts with the lock off 🤦🏻*♂️

The maximum ground speed limit for the A109 with nose wheel unlocked is 20 kts so no-one should be taking taxiway lights or otherwise above that.

I am informed by a friend at Agusta that it is unlikely, but possible, to damage the aircraft if the gear is retracted when the nose wheel is not centered. It has happened. There is no centering cam mechanism and no electronic interlock to prevent the gear from being raised if it is not centered. Most of his colleagues only lock the nose wheel if they are planning on doing rolling takeoffs or landings or taxiing at higher speeds.

The real question one might ask is: How would you explain any damage if you hadn't locked the nose wheel and then retracted the gear?

The A109 doesn't have a self centering nosewheel: at least one VH reg had the wheel hit the bay doors some years ago and cause a bit of damage. The hydraulics won't take the wheel past that first obstruction (the door), but the requirement to lock the nosewheel before takeoff is there for a good reason. A final roll forward should also be made when the lock is engaged to ensure that the NLG is locked before take off.

One pilot I knew, however, steadfastly refused to ever lock the nosewheel as the selection lever in the cockpit dug into his leg while flying when in the lock position :hmm:

If it's not centred and locked prior to takeoff, how are you going to centre and lock it it the air for a running landing?

Once in the wheel well the NLG is aligned: it can't come down in any condition other than centred.

Certainly you should have the lock engaged.

I think you missed my point....which was that of course the nose lock should always be engaged before gear retraction. A running landing can be carried out up to 40 kts ground speed, but the nosewheel must be locked for a ground speed above 20 kts.

I've watched a number of pilots who seem to rely on the nose gear to self centre when lifting from a helipad, rather than taxing forwards slightly to centre it and wondered if they ever bother to lock it properly. Certainly it's possible for the locking lever to be moved to the locked position without the pin engaging.

This might provide the answer to the OP Question. During the shock absorber extension two internal cams become engaged to ensure the wheel centering before landing gear retraction. (MECAER nose landing gear only). After take-off, with weight of helicopter OFF the gear, a double acting spring (located on the rear side of nose cylinder outer case), recenter the nose wheel before landing gear retraction. (MAGNAGHI nose landing gear only). Copied from 109 engineer type rating training course notes

I have always found it strange that wheeled helicopters do not have shimmy dampeners which are so common on their fixed wing brethren. Anyone know why?
Also in the event of a tailrotor problem leading to a high speed run on landing with the nose wheel locked ..if the aircraft departs from the "Straight and Narrow" in spite of energetic differential braking and fervent prayer would not the locked nosewheel impart a rolling moment to the outside of the turn, perhaps leading to a roll over? A question asked but not answered during training. (EC-225)

Just an aside I have heard of nosewheels being retracted on the S-76 while at 90 degrees leading to the nosewheel jamming in the up position.

Who says wheeled helicopters don't have shimmy dampers??

That would be an incorrect statement.

Re -76: The book says, "the nosewheel does not self centre after lift off if it has swiveled about 180° just before lift off. If retracted in this position, the nosewheel jams in the up position, and normal extension is not possible. If the nosewheel is swiveled more than 90°, a slight forward movement is recommended before lift off".

That seems to suggest it will self centre at 90° or less. Never tried it, always ensured it was in the correct position by a taxi forward if in doubt. Only time had the nosewheel jam up was when the oleo didn't extend on lift off, jammed against the hydraulic jack, and bent it in the process. And it has a shimmy damper.

I agree with the above comments about actual in the field practicea it's common to not lock the nose wheel for normal ops.
The shimmy can be significant to "feels like the nose gear is gonna rip off" for running-offs & landings.

We have had multiple issues with damage to the gear doors, some requiring replacement.
Even though the centering works as it should and the gear went into the nose bay- a combination of picking up with an off center nose wheel, low nose strut (in need if servicing), and poor post installation adjustment of gear door position were the problem.

There was a manufacturer's BT some years ago which required a modification to the nose gear doors of later models to avoid damage from contact with the nosewheel assembly. It involved cutting out a small section at the rear end of the doors.

Well some of the ones I have flown do not hence the nosewheel lock.
Sorry for not being specific as to type.

Are you sure about that? IIRC the nose section redesign and the change of the NLG pivot required the doors to be modified to allow the tyre to remain partially 'out in the breeze' when retracted from the 109E onwards. This was done along with the main gear redesign.

Early model (109A, AII and C)

https://s-media-cache-ak0.pinimg.com...13e540f571.jpg

109E onwards:

http://rickinghamphotography.co.uk/s...l__mg_7777.jpg

Hey John, the older models had that limit on nose wheel turning angle (shown by the red line on the gear door) but the E model doesn't have it? or is it that teensy red mark ahead of the pitot tube?

The 76 was better, 360 swivel available.

Well spotted! From my fading brain cells that 'teensy' red line on the nose is the limit mark for the tow bar; the Agusta tow bar comes with a frangible bolt plus a few spares to break at the folding point of the tow bar rather than damage the limit stops. When there were no spare frangible bolts left a spare would be found which never broke, but the tow bar would then bend in a spectacular manner.

http://helihub.com/wordpress/wp-cont...-gpifz1-2x.jpg

I have a small collection of the remains of frangible bolts, alongside the broken tail wheel lock from a Sea King and a few other souvenirs :cool: ;)