Bell 412
Joined: Sep 2002
Posts: 15
Likes: 0
From: middle east
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???
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???
Joined: Feb 2005
Posts: 340
Likes: 1
From: KPHL
As for the controls moving to the neutral point in the event of a double hydraulics failure, we have done these failures in sim, and there is never any movement through any of the controls - they simply freeze in place.
That neutral point of the elastomerics is without any aerodynamic forces, until someone experiences this I don't think we can be sure of what would happen in a full hydraulic failure. I do think that frozen controls is the most likely outcome, but I would expect some feedback.
If the interlock fails, just move the switch that you last moved. Your finger should still be on it.
Some of the AFCUs accelerate quickly to idle from the “about” 35%N1 position.
When I see a range such as 77-85%N2/Nr I usually target the middle of the range. Assuming that there is a reason for the maximum, as there is for the minimum, I choose to avoid both extremes.
Following what the flight manual says, and not strangers on the internet, is a good idea.
Matthew.
Joined: Oct 2003
Posts: 1,030
Likes: 0
From: Over here
Experienced 412 pilots tend to have large right thumbs, from pressing and releasing the interrupt switch repeatedly. I sometimes just keep it pressed down, but get smoother results from pressing it, making a small movement, and releasing it. I never, ever move the cyclic without having the interrupt pressed when in ATT mode. Bell recommends against it, and it seems to confuse the helipilots. I've seen the sim crash when flown against the helipilots. I fly in ATT mode all the time, going to SAS only when on the ground, and I turn the force trim off only for the hydraulics check. Happily, I don't often have to fly a 412 these days.
Joined: Dec 2001
Posts: 1,835
Likes: 3
From: Philadelphia PA
Gomer:
Sounds like someone understood the AFCS!
My only complaint was that the stick forces working against the force trim were too high, and that the system didn't do a really good job of maintaining attitude in the hover. Otherwise, like you, I never turned ATT mode off.
Sounds like someone understood the AFCS!
My only complaint was that the stick forces working against the force trim were too high, and that the system didn't do a really good job of maintaining attitude in the hover. Otherwise, like you, I never turned ATT mode off.
Joined: Oct 2003
Posts: 1,030
Likes: 0
From: Over here
The 412 AFCS doesn't really do a good job of anything. It doesn't maintain attitude for very long in cruise, and seemingly wasn't designed to do much of anything in a hover. It's better than nothing, of course, but it's a rather poor system. IME flying against it is an exercise in futility, but you have to keep a very close eye on it at all times.
Joined: Jun 2007
Posts: 4
Likes: 0
From: somewhere on the globe
Bell 412 : Hyd Failure
Guys , this could be a good debate. Just being curious about how different pilots may have different views about this situation.
Bell 412 ...No. 1 Hyd. failed at 4-5 miles inbound to your airfield .
Would you like to put her down immediately at an "unknown but available" surface in the middle of a town OR would you consider it worth flying her back because you 're only 2 mins from the base?
Bell 412 ...No. 1 Hyd. failed at 4-5 miles inbound to your airfield .
Would you like to put her down immediately at an "unknown but available" surface in the middle of a town
OR would you consider it worth flying her back because you 're only 2 mins from the base?
Joined: Dec 2007
Posts: 253
Likes: 8
From: the land of redemption
BHT 412 RFM says "land as soon as possible" in case of hydraulics failure and everybody knows this rotorcraft can't be driven with both systems OFF.
For me it means I should land as soon as I get in sight of a suitable surface and a congested environment in a town maybe it is not the right place, even if my home base is located there inside.
Personaly I have had a HYD 1 failure at 40kts in landing and nothing appened apart of feeling some hard pedal force as aspected.
No need to brainstom that time.
Maeroda
For me it means I should land as soon as I get in sight of a suitable surface and a congested environment in a town maybe it is not the right place, even if my home base is located there inside.
Personaly I have had a HYD 1 failure at 40kts in landing and nothing appened apart of feeling some hard pedal force as aspected.
No need to brainstom that time.
Maeroda
Joined: Aug 1999
Aviation Qualifications: ATP+Mil
Posts: 4,411
Likes: 83
From: Gold Coast, Australia
Land ASAP.
But.... what altitude are you at? If you're cruising at 5000ft, the descent to your base 4-5 miles away would take the same flight time as a descent to a spot right below you. You are going to reduce control loads as much as possible (no steep turns to spiral down to the nearest spot!), so why not make for home in a steady descent?
But.... if you're at 500ft, then a minute down to the nearest open space is the choice to make
But.... what altitude are you at? If you're cruising at 5000ft, the descent to your base 4-5 miles away would take the same flight time as a descent to a spot right below you. You are going to reduce control loads as much as possible (no steep turns to spiral down to the nearest spot!), so why not make for home in a steady descent?
But.... if you're at 500ft, then a minute down to the nearest open space is the choice to make
Joined: Jun 2007
Posts: 4
Likes: 0
From: somewhere on the globe
Bell 412
We know the helicopter s not flyable with both hyd.s failed.The RFM says it all.
But what are the chances of both failing at the same time?? Aren't they independent systems , Each with its own pump.
Don't we fly the helicopter in case of a OEI?? There is no doubt that if that field was 25 miles away one would choose to select a field and land. The question here is whether it is prudent to land at an unknown place which during short final phase may prove to be not as good as it looked like from above due to wires /cables etc in a town like environment as against going to your airfield which is 5 miles away.
Opinions please..
But what are the chances of both failing at the same time?? Aren't they independent systems , Each with its own pump.
Don't we fly the helicopter in case of a OEI?? There is no doubt that if that field was 25 miles away one would choose to select a field and land. The question here is whether it is prudent to land at an unknown place which during short final phase may prove to be not as good as it looked like from above due to wires /cables etc in a town like environment as against going to your airfield which is 5 miles away.
Opinions please..
Joined: Jul 2001
Posts: 1,383
Likes: 1
From: ...in view of the 'Southern Cross' ...
Mmmmm ....
I thought John Eacott just answered that question for you ... "Airmanship" dear boy!
2 minutes away ... continue ...... any further perhaps have a good think about it !
I thought John Eacott just answered that question for you ... "Airmanship" dear boy!
2 minutes away ... continue ...... any further perhaps have a good think about it !
Joined: Feb 2005
Posts: 340
Likes: 1
From: KPHL
As long as the landing isn't more dangerous than continued flight, then landing where you are is acceptable and probably the right choice. If you are going to continue, consider what you're flying over, keep loads down, and monitor the good system. If anything shows on the second system, then you have absolutely no choice, and you may regret leaving that field behind you.
Joined: Jan 2009
Posts: 10
Likes: 0
From: Jamaica
412EP MR track and Balance
Ive been having several problems with my helo. It just wont track.....it has a horrible lateral vibration in the 60kts letdown and a bit of vert in the 120kts str8 and level flt regime. Ground resonance seems to occur everywhere it has landed. The techs have done almost everything from changing the elastomeric bearings, Xmsn mounts, MR blades, tracking the TR blades. The aircraft also has an overall high frequency vibration within the airframe. Advice anyone??
Joined: Jul 2001
Posts: 1,383
Likes: 1
From: ...in view of the 'Southern Cross' ...
Mmmm ......
With the M/R blades ..... were/are they a matched set or a mixed bag?
Was the Lift Link checked at the same time as the main transmission mounts?
How many hours "time in service" has the machine?
With the M/R blades ..... were/are they a matched set or a mixed bag?
Was the Lift Link checked at the same time as the main transmission mounts?
How many hours "time in service" has the machine?
Joined: Dec 2001
Posts: 1,835
Likes: 3
From: Philadelphia PA
At one point in my brief career at Bell, I was assigned to flying the 'flying whirl stand' Bell 412.
We had a 'rogue' blade that wouldn't track, and in desparation, I had the mechanic watch while I changed airspeed at the same power setting. The blade went way out of track, and we ended up using balance weights against the tab at the outer tab. That worked.
Not sure if that will help your situation, but every little bit helps.
We had a 'rogue' blade that wouldn't track, and in desparation, I had the mechanic watch while I changed airspeed at the same power setting. The blade went way out of track, and we ended up using balance weights against the tab at the outer tab. That worked.
Not sure if that will help your situation, but every little bit helps.
Joined: Feb 2005
Posts: 7
Likes: 0
From: Australia
Food for Thought:
Shilka,
Just for info, we have had an occasion with a B412 which had a Hyd Sys fail and the aircraft was landed ASAP (thankfully) on a beach about 7nm from the field. After shutdown it was noted that lots of Hyd oil under the aircraft. Closer inspection revealed that both Hyd lines had been chaffing together where they run close together up the hell hole and are supposed to be kept separated by Adel Clamps, until one finally perforated with the inevitable result.
The second line was also chaffed almost through the wall thickness. How long would the second system have lasted....how long is a piece of string? But with my luck, I'm sure Murphy would step in and stuff my day......
So I'll treat a system which is grandfather on 1950's technology, which has no decent, well designed Leak/Detection/Isolation system with huge suspicion . Especially when it relies on a serviceable Hyd System to maintain controlled flight and only gives you 2 x systems each which run close beside each other.......too much room for potential problems for my liking.
I think the Huehy system (1 x Hyd sys) was inherently safer, at least you could fly it when it did fail....
Food for Thought......
Shak'n
Just for info, we have had an occasion with a B412 which had a Hyd Sys fail and the aircraft was landed ASAP (thankfully) on a beach about 7nm from the field. After shutdown it was noted that lots of Hyd oil under the aircraft. Closer inspection revealed that both Hyd lines had been chaffing together where they run close together up the hell hole and are supposed to be kept separated by Adel Clamps, until one finally perforated with the inevitable result.
The second line was also chaffed almost through the wall thickness. How long would the second system have lasted....how long is a piece of string? But with my luck, I'm sure Murphy would step in and stuff my day......
So I'll treat a system which is grandfather on 1950's technology, which has no decent, well designed Leak/Detection/Isolation system with huge suspicion . Especially when it relies on a serviceable Hyd System to maintain controlled flight and only gives you 2 x systems each which run close beside each other.......too much room for potential problems for my liking.
I think the Huehy system (1 x Hyd sys) was inherently safer, at least you could fly it when it did fail....
Food for Thought......
Shak'n
Joined: Apr 2006
Posts: 300
Likes: 0
From: USA (PA)
But what are the chances of both failing at the same time?? Aren't they independent systems , Each with its own pump.
Don't we fly the helicopter in case of a OEI?
Don't we fly the helicopter in case of a OEI?
The post above by shak'n seems to prove the point: what's the reason the initial failure happened in the first place? Good airmanship as suggested by John Eacott is key.
Joined: Jan 2009
Posts: 10
Likes: 0
From: turkey
Bell 412 Maintenance Programme
I wonder the maintenance programme of Military 412 helicopters.
Is there any Bell 412 Military operator who is able to explain maintenance programme of military 412 helicopters?
Is there mandatory preflight inspection performed by technicians apart from flight crew performing before each flight?
What is daily inspection consept and validaty?
Is any airframe overhaul (or other type of inspections) scheduled beyond 3000hrs/5year inspections?
Does any military format MM exist for 412 helicopters?
What about maintenance test flight requirements? Do -6CF and -6CL manuals exist for 412 helicopters?
Any help/information will be higly appriciated...
Is there any Bell 412 Military operator who is able to explain maintenance programme of military 412 helicopters?
Is there mandatory preflight inspection performed by technicians apart from flight crew performing before each flight?
What is daily inspection consept and validaty?
Is any airframe overhaul (or other type of inspections) scheduled beyond 3000hrs/5year inspections?
Does any military format MM exist for 412 helicopters?
What about maintenance test flight requirements? Do -6CF and -6CL manuals exist for 412 helicopters?
Any help/information will be higly appriciated...
Joined: Jan 2009
Posts: 10
Likes: 0
From: Jamaica
412EP MR track and balance
A tech rep from Bell Helicopter came and looked at the aircraft. After several checks and isolating the Main drive shaft Vibration. It was realized that the rotor brake disc was warped. That has gotten rid of the high frequency vibration throughout the airframe. The aircraft has subsequently smoothed out a bit. I only experience a slight lateral vibration in the 60 kts letdown.
Joined: Dec 2000
Aviation Qualifications: Non-Aircrew
Posts: 724
Likes: 40
From: Arlington, Tx. US
Deviator
I have seen the reported rotor problems when certain RT&B equipment is being used. What were you using Chadwick, RADS, Bell's HVM?
In most cases it is just a lead-lag damper.
Also unless you have 20 year old blades all are interchangable and not as reported in pairs unless they get cocked up during refurb.
The Sultan
I have seen the reported rotor problems when certain RT&B equipment is being used. What were you using Chadwick, RADS, Bell's HVM?
In most cases it is just a lead-lag damper.
Also unless you have 20 year old blades all are interchangable and not as reported in pairs unless they get cocked up during refurb.
The Sultan
Joined: Dec 2004
Posts: 178
Likes: 5
From: Great White North
Special Inspections for Bell 412 in Military Ops
The answer: NO
All Bell 412s, what ever the paint scheme, have the same inspection requirements. Some customers have elected to slightly modify their schedule because of past incidents/events. And yes, the highest interval is the 5 year/3000 Hr inspection.
All Bell 412s, what ever the paint scheme, have the same inspection requirements. Some customers have elected to slightly modify their schedule because of past incidents/events. And yes, the highest interval is the 5 year/3000 Hr inspection.
