Bell 412 start and performance questions
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Mmmm ...
212s & 412s(with -3B engines) and 412 EPs (with -3D?) engines certainly do start differently.
In the early days the so called 'Okanaghan' start was used because of the problem with the idle stop solenoid activation.
I understood that Bell in their wisdom modified the solenoid so it would operate reliably at a lower voltage but could be jammed by friction of the mechanism if an inexperienced pilot has an issue with the start routine.
After so many years and thousands of hours in the beasties ... (particularly with the 412EP) I now just do a check prior to start to ensure that the throttle IS in Idle Cut Off then hit the starter .... at >12% N1 gently roll the throttle to modulate the start ... the lightoff is gentle very much like with the -3B and under normal conditions acceleration good .... (if the battery or starter dies ... then there is no panic I just roll off back to ICO and all is well) as the monster goes through about 35-40% with a reasonable rate of acceleration I roll thru the stop to the idle position and at >55% disengage the starter .... simple ...
212 Vy was 54 Kts and the 412 around 70 Kts depending on Gross weight etc.
212s & 412s(with -3B engines) and 412 EPs (with -3D?) engines certainly do start differently.
In the early days the so called 'Okanaghan' start was used because of the problem with the idle stop solenoid activation.
I understood that Bell in their wisdom modified the solenoid so it would operate reliably at a lower voltage but could be jammed by friction of the mechanism if an inexperienced pilot has an issue with the start routine.
After so many years and thousands of hours in the beasties ... (particularly with the 412EP) I now just do a check prior to start to ensure that the throttle IS in Idle Cut Off then hit the starter .... at >12% N1 gently roll the throttle to modulate the start ... the lightoff is gentle very much like with the -3B and under normal conditions acceleration good .... (if the battery or starter dies ... then there is no panic I just roll off back to ICO and all is well) as the monster goes through about 35-40% with a reasonable rate of acceleration I roll thru the stop to the idle position and at >55% disengage the starter .... simple ...
212 Vy was 54 Kts and the 412 around 70 Kts depending on Gross weight etc.
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I keep hearing all of the stories about how another operator had a problem with the batteries resulting in a hot start. Would really like to see an incident report that actually says that...
If you do not go above the idle stop and then release the stop and resest the throttle just below the idle stop, then you do NOT KNOW where the throttle is set. You are just guessing....
If you do not go above the idle stop and then release the stop and resest the throttle just below the idle stop, then you do NOT KNOW where the throttle is set. You are just guessing....
Unless you have the delicay of a gorilla, the throttle cam pushing the idle stop is easy enought to feel and there should be no need to go past it.
Spinwing - the 212s I flew had a Vy of 56 kts
Spinwing - the 212s I flew had a Vy of 56 kts
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see these?
Quiz Cards
Quiz Cards
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The ******* Way
Engine starts
Bell Helicopters Textron has devised an alternate Engine Starting technique which has been adopted on all ******* operations. During the start procedure at 12%N1 with Engine Oil Pressure indicating, roll the throttle to slightly below the Flight Idle position (approx. 20 degrees - NG of ENGINE uppermost). If the ITT should rise rapidly during the start, control or "modulate" the temperature with the throttle. At approximately 45% N1, the throttle will need to be advanced slightly to increase the N1 to 61%.
This technique allows a pilot to abort a start at anytime with a simple "off" movement of the throttle to the cut-off position, even if electrical power fails.
Pilots must ensure correct internal battery or external power limitations prior to start.
Trog.
P.S Helibuoy - why would you worry about the WAT graphs for the FM Category A Runway (Part C) profile? you wouldn't ever consider using those - would you?
Bell Helicopters Textron has devised an alternate Engine Starting technique which has been adopted on all ******* operations. During the start procedure at 12%N1 with Engine Oil Pressure indicating, roll the throttle to slightly below the Flight Idle position (approx. 20 degrees - NG of ENGINE uppermost). If the ITT should rise rapidly during the start, control or "modulate" the temperature with the throttle. At approximately 45% N1, the throttle will need to be advanced slightly to increase the N1 to 61%.
This technique allows a pilot to abort a start at anytime with a simple "off" movement of the throttle to the cut-off position, even if electrical power fails.
Pilots must ensure correct internal battery or external power limitations prior to start.
Trog.
P.S Helibuoy - why would you worry about the WAT graphs for the FM Category A Runway (Part C) profile? you wouldn't ever consider using those - would you?
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The only 'incident' I've ever heard of for the 'Throttle pre-positioned to just below idle before hitting start switch' method was when a very new-to-turbine engines pilot was partway through the start and had a loud buzzing noise in his headset. He immediately shut off the start switch without shutting off the throttle.
My friend sitting in the copilot seat watched the TOT go through the roof, and later picked up bits of melted engine off the tarmac. Needless to say, pilot was not long with the company.
My friend sitting in the copilot seat watched the TOT go through the roof, and later picked up bits of melted engine off the tarmac. Needless to say, pilot was not long with the company.
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The only 'incident' I've ever heard of for the 'Throttle pre-positioned to just below idle before hitting start switch' method was when a very new-to-turbine engines pilot was partway through the start and had a loud buzzing noise in his headset. He immediately shut off the start switch without shutting off the throttle.
My friend sitting in the copilot seat watched the TOT go through the roof, and later picked up bits of melted engine off the tarmac. Needless to say, pilot was not long with the company
My friend sitting in the copilot seat watched the TOT go through the roof, and later picked up bits of melted engine off the tarmac. Needless to say, pilot was not long with the company
I wish Bell would clarify this issue, it seems every company I work for has a different start method, and then every pilot has his/her preferred method. I think just to say "refer to the 212/412 RFM" is unhelpful as this does not tell you 100% which side of the idle stop you are at. Two major companies I've worked for use the full open then back to just below idle stop method and I never heard of any problems. But listening to the reasoning of the alternative methods then the argument seems valid. No wonder there are issues with Hot starts, it can be very confusing for newly rated pilots being shown three different methods.
Of the three methods discussed, the only one that really makes sense to me is the so called "Canadian start". Apart from Shawn's example, does anyone know of any reason that this could not be used as standard?
TS
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CAT A Ops
My understanding is that for say Sea Level, 30deg C, deck at or above 90 ft ht when tgt tq was 67%, max Restd AUW was (and is) 11000 lbs.
Now that the tgt tq has increased to 73%, shouldn't there be a corresponding inc in Restd AUW?
Now that the tgt tq has increased to 73%, shouldn't there be a corresponding inc in Restd AUW?
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Cat A Part A?
Helibuoy,
The WAT Graph is only relevant for the climb segment above 200 feet and should not affect your Deck Operating weight.
Compare the graphs for the 3D, 3DE & 3DF engines on the EP - the WAT figures vary but the 2 and a half minute OEI parameter is the same for all 3 variants and this is the parameter used for segments 1 and segment 2 of the profile. Segment 3 (200 feet to 1000 feet) relies on the Max Continuous OEI for the 3D and the 30 minute OEI for the 3DE & 3DF which is why the WAT graphs differ.
For Offshore Ops most Operators use Twin Engine Hover out of Ground Effect (HOGE) graphs to calculate Landing and take-off Mass although the profile flown is similar if not identical to Cat A Part A.
We comply with Performance Class 2 and this is perfectly acceptable to all the Major Oil Companies that I have come across.
2 Engine HOGE for Unrestricted Decks (fully compliant with CAP437/ICAO Annex 14) gives the following figures:
For a basic 412 or 412SP with C Box Torque indication only your MTOM at 30 Deg C is 11400lbs.
For the 412HP or 412EP with Mast Torque indication your MTOM is 11900 at 30 Deg C.
For restricted decks - i.e. not fully compliant due to a whole range of factors we use HOGE minus 500 lbs to give extra power in hand.
Hope this is of some use.
Trog
The WAT Graph is only relevant for the climb segment above 200 feet and should not affect your Deck Operating weight.
Compare the graphs for the 3D, 3DE & 3DF engines on the EP - the WAT figures vary but the 2 and a half minute OEI parameter is the same for all 3 variants and this is the parameter used for segments 1 and segment 2 of the profile. Segment 3 (200 feet to 1000 feet) relies on the Max Continuous OEI for the 3D and the 30 minute OEI for the 3DE & 3DF which is why the WAT graphs differ.
For Offshore Ops most Operators use Twin Engine Hover out of Ground Effect (HOGE) graphs to calculate Landing and take-off Mass although the profile flown is similar if not identical to Cat A Part A.
We comply with Performance Class 2 and this is perfectly acceptable to all the Major Oil Companies that I have come across.
2 Engine HOGE for Unrestricted Decks (fully compliant with CAP437/ICAO Annex 14) gives the following figures:
For a basic 412 or 412SP with C Box Torque indication only your MTOM at 30 Deg C is 11400lbs.
For the 412HP or 412EP with Mast Torque indication your MTOM is 11900 at 30 Deg C.
For restricted decks - i.e. not fully compliant due to a whole range of factors we use HOGE minus 500 lbs to give extra power in hand.
Hope this is of some use.
Trog
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Cat A
Thanks a ton Trog,
The basic difference is that where I'm operating right now ie; India, the DGCA has mandated that all offshore ops have to be Performance Class I (in vogue for more than 4yrs now).
Therefore Cat A, Part A kicks in restricting your load to WAT for Cat A Part A, which works out to 11000lbs (SL, 30deg C) for the EP with DF engines.
I guess this should be directly linked to the tgt tq (the tq that each DF eng is guaranteed to deliver OEI)?
The basic difference is that where I'm operating right now ie; India, the DGCA has mandated that all offshore ops have to be Performance Class I (in vogue for more than 4yrs now).
Therefore Cat A, Part A kicks in restricting your load to WAT for Cat A Part A, which works out to 11000lbs (SL, 30deg C) for the EP with DF engines.
I guess this should be directly linked to the tgt tq (the tq that each DF eng is guaranteed to deliver OEI)?
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Logic Free Zone 2
Helibuoy,
What a waste of a 412 EP.
I haven't been too concerned with the CAT A (Part A) mainly cos' we don't have to be but I still as you do suspect the graphs.
I'll dig a bit deeper in the meantime.
Are you still doing your medical every morning? - What a place!
take care
Trog
What a waste of a 412 EP.
I haven't been too concerned with the CAT A (Part A) mainly cos' we don't have to be but I still as you do suspect the graphs.
I'll dig a bit deeper in the meantime.
Are you still doing your medical every morning? - What a place!
take care
Trog
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Cat A
From what I have gathered so far the whole exercise of Performance Class I of DGCA is to talk Cat A but call it another name....unlike what most Oil companies worldwide follow as 'exposure time' during take off from Rigs etc ...to be able to climb away following a OEI condition..and maybe a similar exposure time during landings Offshore.
True Cat A capability for various machines like S-76 , AW-139 involves a great deal of concept definations,performance issues, helicopter configuration ,training for both Pilots from both seats(to land or take off from Offshore rigs based on obstructions etc ) which probably the DGCA would not like to address or is incapable of analysing with its present members .., nor would the helicopter Operators...so using part of the supplement for Cat A of the Bell 412 ,some details are reduced to some numbers that work for all concerned. I guess a similar number works for the Dauphin N3 or other such machines that operate Offshore.
Serious Regulators would go the extra mile to fully investigate , understand and legislate Cat A issues coz they are liable to legal recourse in many countries not only by the aggreived parties concerned ,but by Insurance companies as well... if they are found wanting .
True Cat A capability for various machines like S-76 , AW-139 involves a great deal of concept definations,performance issues, helicopter configuration ,training for both Pilots from both seats(to land or take off from Offshore rigs based on obstructions etc ) which probably the DGCA would not like to address or is incapable of analysing with its present members .., nor would the helicopter Operators...so using part of the supplement for Cat A of the Bell 412 ,some details are reduced to some numbers that work for all concerned. I guess a similar number works for the Dauphin N3 or other such machines that operate Offshore.
Serious Regulators would go the extra mile to fully investigate , understand and legislate Cat A issues coz they are liable to legal recourse in many countries not only by the aggreived parties concerned ,but by Insurance companies as well... if they are found wanting .
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Cat A
Can you explain target torque and its origin ?...as in the Bell-412 Flight Manual ..Supplement details etc .
One could take a relook and try to understand what you say or question... else just quote verbatim all you see / cut - paste the whole page to better understand what the Bell company allows you to do or wants you to limit yourself to ?? Any data outside of the Bell Manuals I hope you understand is not legal .. except those which are introduced by Operators or Regulators to make Operations safer ?
One could take a relook and try to understand what you say or question... else just quote verbatim all you see / cut - paste the whole page to better understand what the Bell company allows you to do or wants you to limit yourself to ?? Any data outside of the Bell Manuals I hope you understand is not legal .. except those which are introduced by Operators or Regulators to make Operations safer ?
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Cat A
Shawn,
You are the right person to help on the issue of Bell 412 Offshore Operations !!
I tried picking up an earlier post here.. of 18 Jun where Zudhir and helibuoy were trying to understand what is a 'target torque' and related MTOW issues in the Cat A supplement of the Bell 412 ....I don't readily have one so I can't fully understand their apprehensions .
Thanks
Prehar
You are the right person to help on the issue of Bell 412 Offshore Operations !!
I tried picking up an earlier post here.. of 18 Jun where Zudhir and helibuoy were trying to understand what is a 'target torque' and related MTOW issues in the Cat A supplement of the Bell 412 ....I don't readily have one so I can't fully understand their apprehensions .
Thanks
Prehar
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Cat A
Shawn & Prehar,
Well here goes:
I had raised a query with Bell in Feb2009 as follows:
Based on this query, I believe, the Tgt Torque graph was revised last year in Jul2009, shifting the entire graph right and also increasing the max limit to 81%.
With the revised graph the tgt tq has increased (ex 30deg C SL the fig has inc from 67% earlier to 73% now) and so on.
My quest is, with this inc in tgt tq shouldn't there be a corresponding inc in the RTOW for Cat A ops?
Helibuoy
Well here goes:
I had raised a query with Bell in Feb2009 as follows:
Code:
The basic RFM for
Bell 412 EP lays
down the engine torque limit of 81% for 2.5' OEI
operation.
FMS 56.3 & 56.4 for
30' power setting for DF engines retains the same 81% engine torque limit for
2.5' OEI operation.
If you look at the
performance graphs for Target Torque in FMS 62.3 & 62.4 (Cat A operations
with D series engines), the maximum 2.5' engine torque is only 73% at -40
degrees at Sea level. At 20 degrees and 30 degrees we get the figures of 67.5%
and 65%. Since the graph talks of Power Available for 2.5' OEI operation, does
it mean that the power limits of 77% (30') and 81% (2.5') are just figures that
can not be achieved?
With the revised graph the tgt tq has increased (ex 30deg C SL the fig has inc from 67% earlier to 73% now) and so on.
My quest is, with this inc in tgt tq shouldn't there be a corresponding inc in the RTOW for Cat A ops?
Helibuoy
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My quest is, with this inc in tgt tq shouldn't there be a corresponding inc in the RTOW for Cat A ops?
No.
The target torque is Bell’s poor man’s equivalent to a FLI (first limit indicator). Dependant on ambient conditions the first OEI limit the engine is expected to reach, whether engine torque, ITT or N1, is “translated” into a calculated torque value, so in case of an engine failure the pilot has only one power instrument to monitor at what will be a pretty busy time.
This target torque value represents the first OEI 2˝ minute limit to be reached.
As Troglodita pointed out, the climb segment between 200 and 1000 ft AGL is the limiting segment in determining Cat A/PC1 RTOW, and this is flown/certificated at OEI MCP (-3D engines) or OEI 30 min. limits (-3DE and -3DF engines). So the target torque value has nothing to do with the power settings during the “weight limiting” segment of the Cat A profile.
Hope this answers your question adequately.