I must be bored. Try this lot.
A quick check of all 4 Bell 412 Flight Manuals showed the following.
The 85% N2 on the No 2 engine if started first appears only in FM1 (Classic 412).
The others, FM2 412SP, FM3 412HP, FM4 412EP, do NOT mention this bit. The rest of the numbers, 77% to 85%N2/NR etc are common to all 4 manuals. ALTHOUGH the wording in all 4 manuals is slightly different.?????
Personally, I have always gone for the 85% N2. One reason is that I am a convert from the 212 where this is the norm. More importantly, being at 85% N2/NR allows more time and control for a SOFT C Box engagement. Reason - Some of the AFCUs accelerate quickly to idle from the “about” 35%N1 position. This causes the N2 on the second engine to have a corresponding quick acceleration and an UNSOFT engagement if the N2/NR is at 77% on the first engine.
As for SAS vs ATT selection. Just prior to take off I select ATT. I then hold the Force Trim button in for all hovering, take off, until I am stable in the climb, then release. Any time I need to do in flight maneuvering I push the FT button. Come landing time I push the FT button, hold it in till on the ground. The only time I turn it off is when I am on the ground at an intermediate stop or shutting down. I have flown with SOME pilots who never use ATT when VFR and come the Night IFR flying when they MUST use ATT they have trouble remembering when to push the FT button and then we get the cyclic (and helicopter) jumping around. With ATT mode selected, and the FT button is pushed the ATT mode is cancelled BUT the SAS is operating happily. In flight, the moment I release the FT button I get ALL the assistance of the ATT function immediately. I don’t have worry about resetting the ATT selector. No, my thumb does NOT hurt. I cannot imagine, why, if doing any hovering or running landing, with ATT mode selected, the pilot would NOT have the FT button pushed ( and KEEP it pushed till the machine is at rest). It is so much easier to fly that way rather than ‘muscling’ the cyclic around.
Care needs to be taken when making a definitive statement about the 412s. As with the wording on the engine starting numbers, with the different AFCS systems over the 4 different 412s the reactions of the helicopters will be different. The original 412 with the roll oscillations during run on landings says turn off SCAS. The later models say turn off HeliPilots.
Yes, flying the 500, especially on very short sling ops, I would muscle the cyclic around. Mainly because the trim system cannot be cancelled and beeping the cyclic is too slow. The 212/412 have the system that allows the pilot to push the FT button, so, why not.
Re the 3 or 4 412s going into “ ground resonance” hover instability” whatever you want to call it. I believe they were all OLD 412s or 412SPs. NO HPs or EPs. Also, At least 2 of them were operating on training, with BOTH HeliPilots OFF. Any others heard along these lines?
QUESTION. With the 412 shutdown the collective can be raised easily to about half up (the neutral point for the rotor head elastomerics). At this point you CANNOT move the collective up or down. I understand that this is why a single hydraulic system failure is treated as a critical emergency. The machine cannot be flown with both hydraulics out.
What would happen, when doing the 100% NR Hydraulic interlock check, the interlock failed and you end up with BOTH hydraulics OFF.
I think with the rotor turning at 100% the aerodynamic forces would quickly bring the collective to the neutral elastomeric position and you would be in a hover with NO HYDRAULICS. This possibility was pointed out by a Bell production test pilot on loan to our company. Unofficially he suggested doing the interlock check at idle NR.
What you think???