AS 350 SHORT SHAFT FAILURE
 

Has anyone out there ever experienced a short shaft failure in a squirrell before (shaft between the engine and the main gearbox), or have any idea on what will happen there after and the published emergency reaction to it. As I see it, the sudden increase in RPM after the shaft breaks will be felt through the tail rotor. Will the governor react and reduce the RPM back to normal?

You'll get a heavy yaw, the RRPM horn goes off, enter an auto, then what?

1. Do you cut the engine to take away the t/r going nuts and then end up in a side ways position at the end of the flare and a chance of rolling
2. Cut the engine and slide it in with a bit of forward speed keeping the tail fin effective
3. Reduce the fuel flow controlling the amount of thrust to the t/r
4. Keep the engine on during the auto???

So far I can't find anything on this in any manuals...

Edited to remove cr@p once I RTFQ!!

Suggest you may get a transient increase in Ng and T4 while the horn would sound as the Nr decayed. We teach to enter auto and reduce throttle to idle (not sure that the governor would maintain normal tail rotor rpm if not driving the main rotor) then carry out an EOL. Could be difficult to differenciate between this and a governor run down as after the initial (and only possible) rise in N1, the N1 would come down to around the idle figure.

The governor will keep the N2 at 100% (after the transient overspeed due to the rapid unloading).
I've run up several helicopters with no rotor blades and they all governed at 100% with no problems.
The engine governs at 100% in a collective lowered, rotor RPM split descent, doesn't it?

Shawn - good point - I've run the 412 sans blades for a zero tq check and it does govern at 100%. So no need to close the throttle. If that initial spike is missed, how to determine if it's a governor run down or input drive failure (other than to try going into emergency range). I think the engine indications would be similar? Depends how much N1 is needed to drive the tail I suppose.

What will the FCU do when you raise the collective to check RPM in the flare and/or to cushion the landing?

Yeah well pilot stuff aside the major problem will be the shaft breaking would probably whip around and cut the housing which actually holds up the front of the engine.
If that happened the front of the engine would drop and you can forget about FCU this-and-that as all the angles would change to the FCU arms and the Tail Rotor short shaft would probably also separate (that would whip around a fair bit too, good bye tail rotor control rod, boom would probably stay on).
Youd have a lot more problems very quickly.
Id say its not in the flight manual for the same reason blades coming off arent in there .
(Youd probably want to get out before any of this happened)

I remember having read an accident report where an AS 350 pilot had to cope with this failure....He initiared an autorotation to maintain NR, but on flaring, together with collective application, the anticipator increased NG with tail rotor rpm inducing an unexpected yaw at this stage.
It hit trees on landing but the pilot survived his injuries. I think it was a PLM S350 somewhere near Inverness some years back.

Can anybody point me in a direction where to buy a B2/B3 FOM. I wanted to ask here before going to Eurocopter directly.

Thanks,
Ready2Fly

AS-350B3 Survey
 

I would like to hear from:

1. Anyone conducting emergency procedure training in an AS-350B3 equipped with twist grip solenoid (post-MOD 073084 not modified per MOD 073222).

2. Anyone with the same configuration NOT conducting the BFF functional check of the twist grip solenoid spelled out in ASB 05.00.44.

Thanks.

We operate a fleet of 350 BBs with throttles on the collective.. We do not simulate governor failures by reducing Nr below the governed band because the RFM Limitations section only allows Nr at 390 +/- 4. To practice a governor run down/fluctuations would required the Nr to be reduced below the minimum governed. However, I know that the Australian military used to ignore this and use the throttle to practice gov probs and tail rotor malfunctions.

AS350 power margins
 

Hi all

Can some of you clever ones assist here. We operate BA and B2 squirrels on EMS at a standard all up mission weight of say 2050kg. If max TO power is 641 and 732shp respectively, how do we crunch numbers to compare power margin's at takeoff, in % please? :ugh:

My simple view tells me there is a 51shp difference in takeoff power. As a % of the BA power this is 8% more?
As a pilot it seems like the difference is greater than this?
:confused:Whats the go here??

At a guess only -

The 2 numbers you are quoting are the TO ratings of the engine not the MGB.

From memory only there is no difference between MCP and TO power in a B or a BA. 83 and 88 % resp i.e you can fly it all day at TO power - other limitations being considered of course. This equals 532 HP on a B and 564 HP on a BA.

Also in a B2 there is a limitation on MCP and TO power versus speed i.e TO power may only be used up to ~ 40 knots. It probably equates to only being able to use the extra power over a BA in the hover.

The other issue you may have is that the Q meter indications i.e. % versus pressure from the torquemeter may be different on a 1B engine and a 1D1.

Also keep in mind Q for a constant RPM versus collective pitch angle is non linear.

If your question is in response to the NZ CAA slingload with pax operations the "power margin" is virtually impossible to work out with the data you have available. You could be Ng limited - how would you work that out? It would have been much easier if they had imposed a weight margin from the published performance data.

Thanks for the reply. Was hoping for an easy answer but guess nothing is ever easy. I was talking about the engines, isn't the MGB the same and rated for much higher power anyway.
You say 88% Ng = 564hp =MCP=TOP for the BA. Where does the 641hp for TO figure come from that is often published?
Can you use Ng (being the most common first limit reached) and compare the performance of the two that way, somehow??.
Nothing to do with human slingloads which I understand to be limited to 80% of the charted HOGE weight limit. Just trying to be able to say that B2 is ??% more powerful than the BA, at the same AUW using max power available, ie. TO power.

HI!
I am not gonna get into figures here as it is almost impossible to compare the 1D1 and the 1B so direct. It would be the same comparing the 1D1 to the 2B and/or 2B1 on the B3's. We found the easiest way to work out the margins between the various Squirrels is looking at the HOGE graph at 3000ft + and 20 degrees C +. You can use the max all up loss vs height and temp to work out a percentage loss in performance. This is not directly engine related due to the MR and TR blades differences, but then that also tells a story. You can only load your blade twist as much as your engine can drive under all circumstances.

AStar Techniques
 

I thought that everyone might have a little tip for flying the AS 350 Squirrel. I have a few to start things off.

1. Place your left pinky (smallest finger) on the throttle quadrant when adding fuel during the start. You will get much finer control (and fewer T4 "excursions")

2. If you are having trouble with the "squirrely" action of the aircraft in the final metre of landing, shake the cyclic ever so slightly but quickly (like you have Parkinson's disease) and you will grease it on every time. (Be aware that doing this incorrectly could lead to spilling all the lift and even worse dynamic roll over).

3. Can't remember to turn off the landing light? Turn on the switch lights when you turn on the landing/taxi light and this will remind you on shut down.

4. Push on the back of the front door 20 cm up from the bottom and it will close beautifully every time. Higher up near the handle causes the door to distort and be difficult.

5. Make your approach with the nose pointed left and you won't have to peer and strain to see over the dash.

6. Our company wants the tail rotor horizontal when the helicopter is tied down (to prevent water from accumulating and throwing the t/r out of balance) If the t/r is vertical, rotate the main blades 1/3 of a turn and the t/r will be close to horizontal. This only matters if you have the blade to the front tie down system

Interesting, HUH? WTF?

point 6
isn't what those dirty great big holes in the tail rotor for????? I have had snow build up in them but water...:confused:

RE: point 6. Apparently if the t/r is vertical then the water can seep in where the rubber bearings are and make one blade heavier than the other... that is what I am told.