Bell 412
Join Date: Jul 2001
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Mmmmm....
If its giving you trouble check thru the maint records to see if any of the elastomerics have recently been changed.
Some machines with mismatched (ie hard/soft) elastomers have been known to drive mechanics NUTS trying to get them to fly smooth.
Good Luck ....
If its giving you trouble check thru the maint records to see if any of the elastomerics have recently been changed.
Some machines with mismatched (ie hard/soft) elastomers have been known to drive mechanics NUTS trying to get them to fly smooth.
Good Luck ....
Join Date: Jan 2006
Location: Shrewsbury
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Get it the best you can at 62 and 100 before even thinking about a hover. Progress then to the full range (except VNE unless it's very smooth). Edit out the product balance unless it just won't come in without them. On a good day, after component changes, it takes my team about 6 runs on the ground and up to four flights to get the beast in limits. Bonne Chance!
Join Date: Jan 2002
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Whatlimit
There are no short cuts to RTB on the 412 the key is making sure you are using the right program for your aircraft Landing gear (high or Lo gear) and pylon mount configuration.
The donkeywork is done on the ground and the hover using the initial flight plan before attempting the full flight.
The test condition FPOG means Collective FULLY DOWN and not lifted to ease the ground bounce.
Also pay attention to the MM AUM range stated for the procedure as the RADS response sensitivities are set for that AUM.
Here is a list of tips from Chuck Kemp who is the doyen of 412 RADS RTB and another list from Dave Burch from Bell, if these don't answer your questions then you will have to pick up the phone to Mirabel..
Cheers W
"""""
Use the scripts on the following aircraft:
1. 412_41 (For those aircraft with soft pylon mounts (-105) and standard
landing gear low or high.
2. 412F (For those aircraft with soft pylon mounts (-105) and float style
landing gear.
3. 412_50 (For those aircraft with hard pylon mounts (-107) all landing gear
types.
Perform a visual inspection to determine which type of pylon mount
you have. Olive drab green are the soft mounts (-105) and Epoxy Polyamide
Yellow are hard mounts (-107). You also need to determine if you have dual swashplate drive links installed.
If you have single drive links this can give a problem where the ips level
will tend to bias around only one phase angle. Bell gave out dual drive links
for free when they introduced them but some AB412 customers still have
single drive links. If you don't have hard mounts or dual drive links then
you need to get them for a consistent rt&b solution.
If you go into flight with high vibration levels and a track split larger
than 45 mm's the machine is not ready for the forward flight flight plan.
The proper way to perform the initial is:
1. Determine which type of pylon mounts you have and use the appropriate script file
2. Obtain a perfect track of +20 m/m's on RED/BLU and -20 mm's on ORG/GRN +/- 1mm using p/c link at 62% idle. Turn off Tabs, Hub Weights & Product Balance at
this point using the diagnostic editor.
3. Run aircraft at idle and 100%FPG and 100TQ if high gear. Stop track change from idle to 100% using Outboard tabs. Turn off product Balance at this time using the diagnostic editor.
Don't make p/c links changes of less than two flats Don't proceed to Hover
until track change is less than 2 mm's and lateral balance is below 0.2ips (low
skid) or f/a is below 0.2 ips (high skid gear).
4. Now run idle, FPOG, 100TQ and Hover. Stop track change between FPOG and
HOVER using product balance. Hover lateral is not so important here instead we
are interested in stopping the track change. Keep performing this until the
track change is less than 4 mm's or you can't make a product balance move. All
test states should still be in limits. If all are good proceed to forward
flight.
Forward Flight (Soft Mounts using 412_41 or 412F scripts)
1. Perform forward flight taking data at all test states!
2. Set Auto-rotation on very first flight. Setting it last can cause 1 per
rev. and a couple more flights to fix.
3. Look at initial adjustments and predictions. On the first flight you will
probably do what the CADU comes up with.
4. On the second flight usually the verticals are down but you still have some
lateral. If vertical is down turn off Tabs leaving on P/C and Hub Weights.
P/C's will work you lateral in flight and hub weights will work your lateral on
the ground and let down.
Forward Flight (Hard Mounts using 412_50 script)
1. Perform forward flight taking data at all test states
2. Set Auto-rotation on very first flight. Setting it last can cause 1 per
rev. and a couple more flights to fix.
3. CADU will default down to a maximum of 6 adjustments. Usually these are
what you end up using.
4. Instead of playing with edit adjustables, use Max # and adjust that number
up or down to get you favored predictions. This will allow the CADU to pick
adjustments with the maximum effect and not what you think it will need thus
keeping track split close and vibe levels down.""""""""""
And here are extracts from a list of more tips from Bell CSR Dave Burch I hope he doesn't mind my posting it.
"""
412 MAIN ROTOR VIBRATION CHECKLIST
1. Insure that the tail rotor is in track and balance. An out of balance or track tail rotor is often felt as a roughness or a one per rev vibration in the cabin in forward flight and not as a medium (or high) frequency vibration. Feel the left hand elevator at 100% on the ground. Don't take the pilots word for it. Because of the hydraulics most pilots won't feel a tail rotor buzz until it is in the 0.6 IPS range.
2. Insure that the engine to transmission input drive shaft is balanced. The drive shaft will make a pulsating low frequency noise at about 1.25 second intervals in flight that will make the passengers and pilots feel very tired and uncomfortable in flight. This may be perceived as a one per rev vibration. Again many times this will not be noticeable to the pilots as a specific high frequency vibration in the airframe.
3. Wash and wax the blades. The 412 airfoil is very critical. It is not unusual to see 0.2/0.3 IPS vibration changes by just cleaning the blades. Be sure to use non-silicone wax per MIL-W-18723. Insure that the product balance weight pocket covers are sealed properly with no squeeze out above the surface of the blade while insuring that the gap around the pocket cover is filled evenly and smooth with the upper surface of the blade.
4. Inspect the skid gear cap assemblies for condition of the rubber. If the latest dash number elastomer (P/N: 412-030-437-103) are not installed; then they should be at the earliest possible date. Bad or old style (P/N: 412-030-437-101) elastomer/rubber will cause/feed vibrations and make it very difficult to work the rotor. Insure that any caps sent to Lord for rework are reworked to the -103 assembly.
5. Loose doors, cowlings, elevators or external equipment will amplify any vibrations and particularly the four per rev. Insure that they are tight. There are several Technical Bulletins to help reduce the noise and rattles from the doors that should be complied with on older aircraft. The latch pin rods in the hinge panels often rattle against the inside of the panel. These can be covered with plastic tubing which often decreases the cabin noise level considerably.
6. Check the elevators for looseness in the spar to horn and at the horn to fuselage mount bearings. It is necessary to disconnect the spring cartridge in order to check the preload. Be aware that the inspection criteria for axial play in the maintenance manual is currently incorrect.
7. Check that the pilot/co-pilot seats are tight on the rails and that the vertical lock pins or holes are not worn out. Many times the seats will be loose enough to increase the feeling of an acceptable vibration to an unacceptable one.
8. Insure that all the passenger seats and cabinets are tight. In particular, the high back seats used in the EMS sector give false visual clues by the tops moving excessively even though the vibration is not actually there.
9. Insure that there are not any pieces of equipment or cords in the cabin or cockpit area that are loose or can shake or move where they will give false visual clues to the pilots or passengers that there are excessive vibrations when there are none. Map light cords, windshield wipers and fire extinguishers are notorious for this.
10. Insure that all the equipment in the nose compartment is tight and in particular check for loose ballast or batteries. These make very uncomfortable vibrations and make it very difficult to work the rotor.
11. Insure that the hydraulic actuators are tight and aligned properly. Check that the universal bearings on the extension tubes are tight. This is difficult to check with the pitch links connected due to the loads of the elastomerics of the main rotor. Ensure that the pivot bearings on the input levers are tight. Check the lower mount for elongated bushings or worn bearings or bolts.
12. Insure that the minimum collective friction is adjusted correctly. A slight collective bounce will cause a lot of problems. On the 412SP and 412HP be sure that the droop compensator cable is not giving you a false friction.
13. Check the four pylon mounts for sheared rubber or obvious delamination or deterioration. Check the two friction dampers for proper operation and for loose bearings in the damper or the airframe mount. Loose bearings in the dampers or mount and/or bad or soft pylon mounts will increase the sensitivity of the airframe to the point that it may not be possible to get a good ride and really hurt laterals in the let down.
14. Check the lift link for loose bearings and for any damage to the mounts. Insure that the spacer washer is installed between the upper lift link bearing and the inside of the right side of the transmission mount. If this is not installed the link chaffs the mount and makes a thunk with power changes and adds to the four per rev vibration level.
15. Inspect the instrument panel mounting structure for security and tightness. Insure that all the mounting screws are installed and that the side braces are secure and have no cracks (particularly behind the plastic on the door post.) Insure that the glare shield is in good condition with no cracks or looseness. If the frahm damper is still installed on the instrument panel, insure that it is securely mounted and that the springs are in good condition or that it has been locked out.
16. Insure that the trailing edge expandable bolts on the main rotor hub are set for the proper tension and at the proper dimension from the yokes. This is a repetitive problem. If the customer wishes, PSE can authorize replacement of the expandable bolts with the normal bolt, washer and nut combination.
17. On aircraft with the elastomeric control system links, insure that the serrated rod ends and bushings engage properly and the bearings are set at zero preload at full down collective. Refer to the Maintenance Manual.
18. Insure that the collective levers to sleeve pivot bearings are tight and that pins to bearings are shimmed for the proper clamp up.
19. Insure that the collective lever and two swashplate horn universal bearings are tight.
20. Verify that the swashplate support, gimbal ring and inner ring mount bolts, bushings, and bearings are tight and the shims for the supports show no signs of deterioration or looseness of the mount screws.
21. Verify that the droop stops are rigged properly. Insure that the clevis arms are centered on the cams and do not contact the sides of the cams. If necessary, the thru bolts can be loosened and the lower support rotated to center the clevis to cam. Check the bushings for flat spots. Check the bearings for free movement and proper lubrication.
22. Inspect the elastomers carefully in the main rotor hub. Refer to the maintenance manual for inspection criteria. Insure that the spindle bearing to lead-lag damper joint is secure. Check for evidence of the lead-lag damper working in the damper bridge. Insure that the through bolts are tight and there is no evidence of the yokes moving on the center drive hub or upper or lower cone seats.
23. Insure that any cracks or erosion in the finish of the main rotor blade are filled properly. These can allow water intrusion into the core of the blade which will cause the blade to become unworkable. Check for cracks in the trim tabs or the tab mounting area. Check that the tabs have not lost their rigidity (become soft tabs) that will not hold their settings.
24. If the blades have been reworked, insure that the Bell Helicopter procedures were followed for sanding, repairs, rework, refinishing and re- balancing of the blades. Improperly reworked blades may not be able to behave properly in flight.
25. Insure that the simple pendulum absorbers are lubricated and that the bearings are free. Check by pulling outboard and aft on the weight arms and then check for roughness of the bearings or excessive fore and aft movement.
Hub Weights:
Maximum:
* 8 weights any location.
* 16 weights per yoke end.
Once you get to eight weights on trailing edge add to leading edge.
Product Balance:
Trailing edge weight adjustment does all the track change from ground to hover.
Leading edge balance pocket is just to offset the weight move to keep span wise balance equal.
* 1 weight move= 0.5 IPS hover lateral
* 1/2 weight move=4mm-5mm track change ground to hover
Standard Load:
Leading edge pocket: 135 grams (One thick flat and one thin flat washer)
Trailing edge pocket: 158 grams (One wedge and one thin flat washer)
Ratios:
Trailing edge to leading edge x 0.85
Leading edge to trailing edge x 1.17
It takes approximately nine (9) grams at the hub weight mount arm to offset a one (1) gram mistake at the trailing edge product balance pocket. It takes approximately ten and one half (10.5) grams at the hub weight arm to offset one (1) gram at the leading edge product balance pocket
412 Rotor Working Information
Try to work rotor at 800 to 1200 pounds of fuel, External Auxiliary Fuel Tanks empty and no more than three people on board. Make sure inboard tabs are set to zero before tracking.
On Initial:
1. Get maximum of 2mm track change between 62% FPG and 100% FPG.
If possible, get maximum of 4mm track change or less between 100% FPG and hover.
2. Try for total maximum change between 62% FPG and hover of 4mm if at all possible.
3. Initial does not work lateral in hover, only works track at 62%, 100% and hover and lateral at 100FPG on "412 F & 412_41" programs and fore/aft at 100TQ on the "412_50" program.
4. RADS phase angle is plus 62.5 degrees of the standard Chadwick to compare to charts. (2:00-2:15 on RADS is 12:00 on Chadwick charts, or 12:00 Chadwick = 62.5 degrees (RADS)
5. Concentrate on vertical on first flight before lateral.
6. Significant change in ride level with changes in gross weight indicate a product balance problem or bad rubber.
7. 412 normally indicates 19% to 21% torque at flat pitch on the ground if autorotation is correct. Check Auto rotation RPM on flight, first. Do not make rotor smoothing adjustments until auto revs are set.
8. When getting close to completing a rotor, turn tabs off (412F & 412_41). Concentrate on roll and hub weights.
9. Significant phase angle change from ground to hover indicates product balance needed. Watch phase angles for proper directions of move.
10. Excessive inboard tab may cause ground bounce.
11. Worn swashplate gimbal ring bearings or bores may show up as a lateral in let down.
12. Sudden severe lateral on pickup to a hover is probably a hung droop stop.
13. If you have shifting weight clock angle call out, then look at the opposite pair of blades lead lag dampers.
412_50 ver 5.3 or higher
This program differs in that it has a couple of states that are different than 412_41.
Listed below are the extra states:
1. 100TQ - This is 100% NR on the ground with 5% torque pulled in from the flat pitch reading. With the -107 mounts the aircraft may have more of a ground bounce than a standard aircraft. This will reduce ground bounce and allow you to balance the rotor.
2. 120/97 - This is 120 KIAS with the rotor beeped back to 97% Nr. This state can be skipped until your last flight. No rotor smoothing is accomplished with this reading. (Do not forget to beep back to 100% Nr upon completion!)
This program works diagnostics differently than 412F. It will automatically count down to the smallest amount of adjustments, usually about 6. You can do those adjustments or go into the "edit defaults" on the diagnostic menu.
Once there, turn the best number of adjustments to best 04 and "resolve to limits" off. Press DO, it will then give you the best 4 adjustments or less that will make the rotor smoother. Check the predictions if it is better than "default moves", do those. Try best 3 or 2 moves, they may be better. Just be careful and do not get caught up in trying to reduce the predictions that you are just dropping the vibrations .05 ips between the different adjustments. You are finished when the screen says you are below all set limits or you cannot obtain a smoother ride.
Installation: Install the RADS for 412F ver 1.40 the same as the Bell maintenance manual chapter 65, Install the RADS for 412_50 ver 5.3 the same as above but add a fore/aft accelerometer on the bottom of the instrument panel under the lateral accelerometer. The connector must point fwd. Attach it to channel 3. Reference Technical Bulletin 412-92-111 Rev. A.
412_41 ver 5.3
This program works the same as 412F ver 1.4 yet is to be used on soft mounted aircraft without external tanks and floats
Using The RADS At Night: Install the reflective tape supplied with the kit on the bottom of all four blades trailing edge. It must start at 9" inboard of the mid span tab and be 24" long. Turn the Day/Night test knob on the DAU to "Night."
Using a mini mag light ( something with a small focused beam ) align it with the UTD and adjust the angle of the UTD so that the beam of light hits the middle of the tape. (67 degrees from co-pilots seat rail) You are now ready to track at night!
Common Rotor Adjustment Mistakes: The RADS will only give hub weight adjustments for blue/org blades. If you have weight on red/green don't add to blue/org. Just remove from red/green. Mid span tabs move the blade about the same as outboard. You can use these to adjust track in lieu of outboard tab. Make sure you are not adjusting it opposite of the outboard tab and you are using the correct scale on the tab tool. Do not use inboard tabs. It may or may not work. It's not worth the gamble if you are getting the aircraft smooth without them.
If you have not made the aircraft significantly smoother in 4 or 5 flights, you have a problem. Start checking for loose drive link bearings, loose p/c link bearings, bad rubber, etc. All the bearings (hard) are .007 radial and .015 axial play. If all of these bearings are loose, they add up to a lot of play, which can make your job harder to accomplish.
On a freshly installed M/R head make sure that you retorque between each flight until bolts do not move.
To be certain which program you should use visually check to see which pylon mounts are installed. Hard mounts (-107's) are yellow and Soft mounts (-105's) are green.
You will be better prepared if you will watch the video tape titled "412 Rotor Inspection and Troubleshooting/Rotor Analysis and Diagnostic System", Chapter 65-03-00 through 65-05-00 of the Bell Maintenance Manual. and the Operators Manual supplied with each RADS. There is quite a bit of data that you could find useful in working 412 Rotors...
There are no short cuts to RTB on the 412 the key is making sure you are using the right program for your aircraft Landing gear (high or Lo gear) and pylon mount configuration.
The donkeywork is done on the ground and the hover using the initial flight plan before attempting the full flight.
The test condition FPOG means Collective FULLY DOWN and not lifted to ease the ground bounce.
Also pay attention to the MM AUM range stated for the procedure as the RADS response sensitivities are set for that AUM.
Here is a list of tips from Chuck Kemp who is the doyen of 412 RADS RTB and another list from Dave Burch from Bell, if these don't answer your questions then you will have to pick up the phone to Mirabel..
Cheers W
"""""
Use the scripts on the following aircraft:
1. 412_41 (For those aircraft with soft pylon mounts (-105) and standard
landing gear low or high.
2. 412F (For those aircraft with soft pylon mounts (-105) and float style
landing gear.
3. 412_50 (For those aircraft with hard pylon mounts (-107) all landing gear
types.
Perform a visual inspection to determine which type of pylon mount
you have. Olive drab green are the soft mounts (-105) and Epoxy Polyamide
Yellow are hard mounts (-107). You also need to determine if you have dual swashplate drive links installed.
If you have single drive links this can give a problem where the ips level
will tend to bias around only one phase angle. Bell gave out dual drive links
for free when they introduced them but some AB412 customers still have
single drive links. If you don't have hard mounts or dual drive links then
you need to get them for a consistent rt&b solution.
If you go into flight with high vibration levels and a track split larger
than 45 mm's the machine is not ready for the forward flight flight plan.
The proper way to perform the initial is:
1. Determine which type of pylon mounts you have and use the appropriate script file
2. Obtain a perfect track of +20 m/m's on RED/BLU and -20 mm's on ORG/GRN +/- 1mm using p/c link at 62% idle. Turn off Tabs, Hub Weights & Product Balance at
this point using the diagnostic editor.
3. Run aircraft at idle and 100%FPG and 100TQ if high gear. Stop track change from idle to 100% using Outboard tabs. Turn off product Balance at this time using the diagnostic editor.
Don't make p/c links changes of less than two flats Don't proceed to Hover
until track change is less than 2 mm's and lateral balance is below 0.2ips (low
skid) or f/a is below 0.2 ips (high skid gear).
4. Now run idle, FPOG, 100TQ and Hover. Stop track change between FPOG and
HOVER using product balance. Hover lateral is not so important here instead we
are interested in stopping the track change. Keep performing this until the
track change is less than 4 mm's or you can't make a product balance move. All
test states should still be in limits. If all are good proceed to forward
flight.
Forward Flight (Soft Mounts using 412_41 or 412F scripts)
1. Perform forward flight taking data at all test states!
2. Set Auto-rotation on very first flight. Setting it last can cause 1 per
rev. and a couple more flights to fix.
3. Look at initial adjustments and predictions. On the first flight you will
probably do what the CADU comes up with.
4. On the second flight usually the verticals are down but you still have some
lateral. If vertical is down turn off Tabs leaving on P/C and Hub Weights.
P/C's will work you lateral in flight and hub weights will work your lateral on
the ground and let down.
Forward Flight (Hard Mounts using 412_50 script)
1. Perform forward flight taking data at all test states
2. Set Auto-rotation on very first flight. Setting it last can cause 1 per
rev. and a couple more flights to fix.
3. CADU will default down to a maximum of 6 adjustments. Usually these are
what you end up using.
4. Instead of playing with edit adjustables, use Max # and adjust that number
up or down to get you favored predictions. This will allow the CADU to pick
adjustments with the maximum effect and not what you think it will need thus
keeping track split close and vibe levels down.""""""""""
And here are extracts from a list of more tips from Bell CSR Dave Burch I hope he doesn't mind my posting it.
"""
412 MAIN ROTOR VIBRATION CHECKLIST
1. Insure that the tail rotor is in track and balance. An out of balance or track tail rotor is often felt as a roughness or a one per rev vibration in the cabin in forward flight and not as a medium (or high) frequency vibration. Feel the left hand elevator at 100% on the ground. Don't take the pilots word for it. Because of the hydraulics most pilots won't feel a tail rotor buzz until it is in the 0.6 IPS range.
2. Insure that the engine to transmission input drive shaft is balanced. The drive shaft will make a pulsating low frequency noise at about 1.25 second intervals in flight that will make the passengers and pilots feel very tired and uncomfortable in flight. This may be perceived as a one per rev vibration. Again many times this will not be noticeable to the pilots as a specific high frequency vibration in the airframe.
3. Wash and wax the blades. The 412 airfoil is very critical. It is not unusual to see 0.2/0.3 IPS vibration changes by just cleaning the blades. Be sure to use non-silicone wax per MIL-W-18723. Insure that the product balance weight pocket covers are sealed properly with no squeeze out above the surface of the blade while insuring that the gap around the pocket cover is filled evenly and smooth with the upper surface of the blade.
4. Inspect the skid gear cap assemblies for condition of the rubber. If the latest dash number elastomer (P/N: 412-030-437-103) are not installed; then they should be at the earliest possible date. Bad or old style (P/N: 412-030-437-101) elastomer/rubber will cause/feed vibrations and make it very difficult to work the rotor. Insure that any caps sent to Lord for rework are reworked to the -103 assembly.
5. Loose doors, cowlings, elevators or external equipment will amplify any vibrations and particularly the four per rev. Insure that they are tight. There are several Technical Bulletins to help reduce the noise and rattles from the doors that should be complied with on older aircraft. The latch pin rods in the hinge panels often rattle against the inside of the panel. These can be covered with plastic tubing which often decreases the cabin noise level considerably.
6. Check the elevators for looseness in the spar to horn and at the horn to fuselage mount bearings. It is necessary to disconnect the spring cartridge in order to check the preload. Be aware that the inspection criteria for axial play in the maintenance manual is currently incorrect.
7. Check that the pilot/co-pilot seats are tight on the rails and that the vertical lock pins or holes are not worn out. Many times the seats will be loose enough to increase the feeling of an acceptable vibration to an unacceptable one.
8. Insure that all the passenger seats and cabinets are tight. In particular, the high back seats used in the EMS sector give false visual clues by the tops moving excessively even though the vibration is not actually there.
9. Insure that there are not any pieces of equipment or cords in the cabin or cockpit area that are loose or can shake or move where they will give false visual clues to the pilots or passengers that there are excessive vibrations when there are none. Map light cords, windshield wipers and fire extinguishers are notorious for this.
10. Insure that all the equipment in the nose compartment is tight and in particular check for loose ballast or batteries. These make very uncomfortable vibrations and make it very difficult to work the rotor.
11. Insure that the hydraulic actuators are tight and aligned properly. Check that the universal bearings on the extension tubes are tight. This is difficult to check with the pitch links connected due to the loads of the elastomerics of the main rotor. Ensure that the pivot bearings on the input levers are tight. Check the lower mount for elongated bushings or worn bearings or bolts.
12. Insure that the minimum collective friction is adjusted correctly. A slight collective bounce will cause a lot of problems. On the 412SP and 412HP be sure that the droop compensator cable is not giving you a false friction.
13. Check the four pylon mounts for sheared rubber or obvious delamination or deterioration. Check the two friction dampers for proper operation and for loose bearings in the damper or the airframe mount. Loose bearings in the dampers or mount and/or bad or soft pylon mounts will increase the sensitivity of the airframe to the point that it may not be possible to get a good ride and really hurt laterals in the let down.
14. Check the lift link for loose bearings and for any damage to the mounts. Insure that the spacer washer is installed between the upper lift link bearing and the inside of the right side of the transmission mount. If this is not installed the link chaffs the mount and makes a thunk with power changes and adds to the four per rev vibration level.
15. Inspect the instrument panel mounting structure for security and tightness. Insure that all the mounting screws are installed and that the side braces are secure and have no cracks (particularly behind the plastic on the door post.) Insure that the glare shield is in good condition with no cracks or looseness. If the frahm damper is still installed on the instrument panel, insure that it is securely mounted and that the springs are in good condition or that it has been locked out.
16. Insure that the trailing edge expandable bolts on the main rotor hub are set for the proper tension and at the proper dimension from the yokes. This is a repetitive problem. If the customer wishes, PSE can authorize replacement of the expandable bolts with the normal bolt, washer and nut combination.
17. On aircraft with the elastomeric control system links, insure that the serrated rod ends and bushings engage properly and the bearings are set at zero preload at full down collective. Refer to the Maintenance Manual.
18. Insure that the collective levers to sleeve pivot bearings are tight and that pins to bearings are shimmed for the proper clamp up.
19. Insure that the collective lever and two swashplate horn universal bearings are tight.
20. Verify that the swashplate support, gimbal ring and inner ring mount bolts, bushings, and bearings are tight and the shims for the supports show no signs of deterioration or looseness of the mount screws.
21. Verify that the droop stops are rigged properly. Insure that the clevis arms are centered on the cams and do not contact the sides of the cams. If necessary, the thru bolts can be loosened and the lower support rotated to center the clevis to cam. Check the bushings for flat spots. Check the bearings for free movement and proper lubrication.
22. Inspect the elastomers carefully in the main rotor hub. Refer to the maintenance manual for inspection criteria. Insure that the spindle bearing to lead-lag damper joint is secure. Check for evidence of the lead-lag damper working in the damper bridge. Insure that the through bolts are tight and there is no evidence of the yokes moving on the center drive hub or upper or lower cone seats.
23. Insure that any cracks or erosion in the finish of the main rotor blade are filled properly. These can allow water intrusion into the core of the blade which will cause the blade to become unworkable. Check for cracks in the trim tabs or the tab mounting area. Check that the tabs have not lost their rigidity (become soft tabs) that will not hold their settings.
24. If the blades have been reworked, insure that the Bell Helicopter procedures were followed for sanding, repairs, rework, refinishing and re- balancing of the blades. Improperly reworked blades may not be able to behave properly in flight.
25. Insure that the simple pendulum absorbers are lubricated and that the bearings are free. Check by pulling outboard and aft on the weight arms and then check for roughness of the bearings or excessive fore and aft movement.
Hub Weights:
Maximum:
* 8 weights any location.
* 16 weights per yoke end.
Once you get to eight weights on trailing edge add to leading edge.
Product Balance:
Trailing edge weight adjustment does all the track change from ground to hover.
Leading edge balance pocket is just to offset the weight move to keep span wise balance equal.
* 1 weight move= 0.5 IPS hover lateral
* 1/2 weight move=4mm-5mm track change ground to hover
Standard Load:
Leading edge pocket: 135 grams (One thick flat and one thin flat washer)
Trailing edge pocket: 158 grams (One wedge and one thin flat washer)
Ratios:
Trailing edge to leading edge x 0.85
Leading edge to trailing edge x 1.17
It takes approximately nine (9) grams at the hub weight mount arm to offset a one (1) gram mistake at the trailing edge product balance pocket. It takes approximately ten and one half (10.5) grams at the hub weight arm to offset one (1) gram at the leading edge product balance pocket
412 Rotor Working Information
Try to work rotor at 800 to 1200 pounds of fuel, External Auxiliary Fuel Tanks empty and no more than three people on board. Make sure inboard tabs are set to zero before tracking.
On Initial:
1. Get maximum of 2mm track change between 62% FPG and 100% FPG.
If possible, get maximum of 4mm track change or less between 100% FPG and hover.
2. Try for total maximum change between 62% FPG and hover of 4mm if at all possible.
3. Initial does not work lateral in hover, only works track at 62%, 100% and hover and lateral at 100FPG on "412 F & 412_41" programs and fore/aft at 100TQ on the "412_50" program.
4. RADS phase angle is plus 62.5 degrees of the standard Chadwick to compare to charts. (2:00-2:15 on RADS is 12:00 on Chadwick charts, or 12:00 Chadwick = 62.5 degrees (RADS)
5. Concentrate on vertical on first flight before lateral.
6. Significant change in ride level with changes in gross weight indicate a product balance problem or bad rubber.
7. 412 normally indicates 19% to 21% torque at flat pitch on the ground if autorotation is correct. Check Auto rotation RPM on flight, first. Do not make rotor smoothing adjustments until auto revs are set.
8. When getting close to completing a rotor, turn tabs off (412F & 412_41). Concentrate on roll and hub weights.
9. Significant phase angle change from ground to hover indicates product balance needed. Watch phase angles for proper directions of move.
10. Excessive inboard tab may cause ground bounce.
11. Worn swashplate gimbal ring bearings or bores may show up as a lateral in let down.
12. Sudden severe lateral on pickup to a hover is probably a hung droop stop.
13. If you have shifting weight clock angle call out, then look at the opposite pair of blades lead lag dampers.
412_50 ver 5.3 or higher
This program differs in that it has a couple of states that are different than 412_41.
Listed below are the extra states:
1. 100TQ - This is 100% NR on the ground with 5% torque pulled in from the flat pitch reading. With the -107 mounts the aircraft may have more of a ground bounce than a standard aircraft. This will reduce ground bounce and allow you to balance the rotor.
2. 120/97 - This is 120 KIAS with the rotor beeped back to 97% Nr. This state can be skipped until your last flight. No rotor smoothing is accomplished with this reading. (Do not forget to beep back to 100% Nr upon completion!)
This program works diagnostics differently than 412F. It will automatically count down to the smallest amount of adjustments, usually about 6. You can do those adjustments or go into the "edit defaults" on the diagnostic menu.
Once there, turn the best number of adjustments to best 04 and "resolve to limits" off. Press DO, it will then give you the best 4 adjustments or less that will make the rotor smoother. Check the predictions if it is better than "default moves", do those. Try best 3 or 2 moves, they may be better. Just be careful and do not get caught up in trying to reduce the predictions that you are just dropping the vibrations .05 ips between the different adjustments. You are finished when the screen says you are below all set limits or you cannot obtain a smoother ride.
Installation: Install the RADS for 412F ver 1.40 the same as the Bell maintenance manual chapter 65, Install the RADS for 412_50 ver 5.3 the same as above but add a fore/aft accelerometer on the bottom of the instrument panel under the lateral accelerometer. The connector must point fwd. Attach it to channel 3. Reference Technical Bulletin 412-92-111 Rev. A.
412_41 ver 5.3
This program works the same as 412F ver 1.4 yet is to be used on soft mounted aircraft without external tanks and floats
Using The RADS At Night: Install the reflective tape supplied with the kit on the bottom of all four blades trailing edge. It must start at 9" inboard of the mid span tab and be 24" long. Turn the Day/Night test knob on the DAU to "Night."
Using a mini mag light ( something with a small focused beam ) align it with the UTD and adjust the angle of the UTD so that the beam of light hits the middle of the tape. (67 degrees from co-pilots seat rail) You are now ready to track at night!
Common Rotor Adjustment Mistakes: The RADS will only give hub weight adjustments for blue/org blades. If you have weight on red/green don't add to blue/org. Just remove from red/green. Mid span tabs move the blade about the same as outboard. You can use these to adjust track in lieu of outboard tab. Make sure you are not adjusting it opposite of the outboard tab and you are using the correct scale on the tab tool. Do not use inboard tabs. It may or may not work. It's not worth the gamble if you are getting the aircraft smooth without them.
If you have not made the aircraft significantly smoother in 4 or 5 flights, you have a problem. Start checking for loose drive link bearings, loose p/c link bearings, bad rubber, etc. All the bearings (hard) are .007 radial and .015 axial play. If all of these bearings are loose, they add up to a lot of play, which can make your job harder to accomplish.
On a freshly installed M/R head make sure that you retorque between each flight until bolts do not move.
To be certain which program you should use visually check to see which pylon mounts are installed. Hard mounts (-107's) are yellow and Soft mounts (-105's) are green.
You will be better prepared if you will watch the video tape titled "412 Rotor Inspection and Troubleshooting/Rotor Analysis and Diagnostic System", Chapter 65-03-00 through 65-05-00 of the Bell Maintenance Manual. and the Operators Manual supplied with each RADS. There is quite a bit of data that you could find useful in working 412 Rotors...
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tongue-in-cheek comments on Bell 412 website
Off-the-wall cute obscure website urls, V.1.
www.onefinalcoat.com
Now, would you think that had to do with helicopters? Guess again--it's Bell's 412 LUH advertisement! The "onefinalcoat" turns out to be the hypnotic suggestion that it has everything you could possibly need except that one final coat of your paint scheme!
Some chuckles available on the tech specifications .pdf button, also: the 412 is "based on the four-rotor, twin-engine 412EP" -- wow FOUR ROTORS, what a lifter! Somebody didn't proof-read this, helicopters with 4 rotors are significantly rare in history. (A few lines down they do get to "4-bladed rotor" but that comes after you're fininshed ROFL.)
In a masterstroke of customer reassurance, the Cabin Size options include either 6 or 8 "crashworthy seats." Nice to know, isn't it, that they are subliminally putting you on alert that you WILL crash! Other helicopters, one presumes, have seats not worthy of crashing. Or, perhaps, all the seats are good for is crashing?
The ship "routinely performs multiple same-day missions." How unusual for a helicopter. Must be in contrast to the OTHER helicopters that only do one mission a day? Who wrote this thing?
"Titanium yoke for smoother ride." Hey, everybody should have a titanium yoke, smooths out all those obnoxious jolts and bumps, finaly a smooth-as-silk helicopter.
OK, rant completed, we now return control of your browser to you.
www.onefinalcoat.com
Now, would you think that had to do with helicopters? Guess again--it's Bell's 412 LUH advertisement! The "onefinalcoat" turns out to be the hypnotic suggestion that it has everything you could possibly need except that one final coat of your paint scheme!
Some chuckles available on the tech specifications .pdf button, also: the 412 is "based on the four-rotor, twin-engine 412EP" -- wow FOUR ROTORS, what a lifter! Somebody didn't proof-read this, helicopters with 4 rotors are significantly rare in history. (A few lines down they do get to "4-bladed rotor" but that comes after you're fininshed ROFL.)
In a masterstroke of customer reassurance, the Cabin Size options include either 6 or 8 "crashworthy seats." Nice to know, isn't it, that they are subliminally putting you on alert that you WILL crash! Other helicopters, one presumes, have seats not worthy of crashing. Or, perhaps, all the seats are good for is crashing?
The ship "routinely performs multiple same-day missions." How unusual for a helicopter. Must be in contrast to the OTHER helicopters that only do one mission a day? Who wrote this thing?
"Titanium yoke for smoother ride." Hey, everybody should have a titanium yoke, smooths out all those obnoxious jolts and bumps, finaly a smooth-as-silk helicopter.
OK, rant completed, we now return control of your browser to you.
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Bell 412EP
In 1997 or therabouts, the titanium yoke on a Gulf Helicopters machine, Doha, Qatar broke, whilst proceeding offshore. They all survived, surprisingly enough, although if they had been any higher than approx.1,500' agl they probably wouldn't be here now.
The pilot was a Kiwi who's now resident in Perth, WA, I believe. If he's reading this sometime, could he give me a PM & refresh my memory regarding the registration of this machine & the date of the accident?
Yours aye, airspeed alive
The pilot was a Kiwi who's now resident in Perth, WA, I believe. If he's reading this sometime, could he give me a PM & refresh my memory regarding the registration of this machine & the date of the accident?
Yours aye, airspeed alive
I liked the "ambulatory attendant" comment. Reckon that is opposed to a "non-ambulatory attendant".
This was probably written by a Texan afterall.
This was probably written by a Texan afterall.
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free US ARMY stencil !
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Bell 412 start up with engine air inlet covers on ...
Just a simple question about the topic above: if experienced a start up wihout removing one or both of the engine air inlet covers what actions should be taken before the next flight?
I was told that it depends wether the ITT has exceeded the maximum permitted temperature or not and I was told also that there is a standard procedure on the manual dealing exactly with this case more than explaining what to do in case of a "normal" FOD during the start up or the flight.
I've looked all the documents I got in order to find this specific procedure but I found nothing ...
Does anyone of you has ever experienced this kind of issue and is aware of the correct procedure to follow and where I can find it ?
I hope not to be OT ...
... by the way it's a very important point to discuss about do you agree with me ? 
Thanks a lot to you all,
Sax
I was told that it depends wether the ITT has exceeded the maximum permitted temperature or not and I was told also that there is a standard procedure on the manual dealing exactly with this case more than explaining what to do in case of a "normal" FOD during the start up or the flight.
I've looked all the documents I got in order to find this specific procedure but I found nothing ...
Does anyone of you has ever experienced this kind of issue and is aware of the correct procedure to follow and where I can find it ?
I hope not to be OT ...
... by the way it's a very important point to discuss about do you agree with me ? Thanks a lot to you all,
Sax
Step one would be to firmly kick some butts about the ramp for being stupid!
I would worry first about basic safety procedures and adherence to checklist requirements before starting engines.
At first glance, however, it would seem a standard FOD inspection would suffice assuming the ITT and other start parameters were not exceeded.
Some of our Techie friends might have better ideas and hopefully will pass them along.
I would worry first about basic safety procedures and adherence to checklist requirements before starting engines.
At first glance, however, it would seem a standard FOD inspection would suffice assuming the ITT and other start parameters were not exceeded.
Some of our Techie friends might have better ideas and hopefully will pass them along.
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... I forgot to tell that even if ITT and other limits were not exceeded a good part of the cover had gone into the engine air inlet. Part of it stopped on the net at the entrance of the turbine but where is the missing part we hadn't find? has it been expelled out of the turbine or it's stucked somewhere in some compressor's stage?
The actions taken have been: removal of the cover's part melted and stucked on the first air filter, visual check just of the first air compressor stage, start up and power check and 15' test flight.
I'm wondering if this actions suffice or if the turbine should be further checked opening it to be sure no parts of the cover got stacked inside the engine ... I'm know I'm a little bit too much strict but , you know, 110 miles on the sea during day or night time need this kind of issue to be fixed for sure!
The actions taken have been: removal of the cover's part melted and stucked on the first air filter, visual check just of the first air compressor stage, start up and power check and 15' test flight.
I'm wondering if this actions suffice or if the turbine should be further checked opening it to be sure no parts of the cover got stacked inside the engine ... I'm know I'm a little bit too much strict but , you know, 110 miles on the sea during day or night time need this kind of issue to be fixed for sure!
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Try not to turn it into an issue of cost. If you are concerned that some of the cover has gone into the engine then the ONLY course of action I believe is to have the engine opened up to check for damage and/or remaining debris. Otherwise you will never know and you are risking the lives of all those that fly in it as either crew or pax. Made doubly more important if you are doing long sea transits where quick landing options are significantly reduced. But thats just my opinion....
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The point is that I fully agree with you but I'm not in charge of anything more than stressing as much as I can the possible negative sides of the story ... so also for me this is just my point of view!
Thank you very much though!
Thank you very much though!
There are no limits
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So make an entry in the technical log along the lines of ' Suspect FOD to engine no 1 during start'
Then an engineer has to do something and everyone is covered.
Then an engineer has to do something and everyone is covered.
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To prevent recurrence, tell the pilots to count the rivets on the particle bypass doors during the pre-flight. If they can't count them, then tell them to remove the inlet plugs.
Although this seems like an easy one to avoid, once you're seated in the cockpit it's not an easy one to diagnose. Failure to light may be the only symptom you notice, so you go through a dry run then a second start attempt. Maybe you even decide to try the other engine to get a generator online before you go through that process on the first engine. Point is, its a simple cause but can lead to costly outcome.
Although this seems like an easy one to avoid, once you're seated in the cockpit it's not an easy one to diagnose. Failure to light may be the only symptom you notice, so you go through a dry run then a second start attempt. Maybe you even decide to try the other engine to get a generator online before you go through that process on the first engine. Point is, its a simple cause but can lead to costly outcome.
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An engineer has already performed some check, the point is if these checks are all what he shoud have done or not... that's it!
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Simple then - tell the engineer and your boss that you want them to accompany you on the next flight and tell them it will be a long over sea night transit. If they start squirming and making excuses about not wanting to be home late for dinner then strongly suggest a second opinion from the engine manufacturer is sought.....
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Hey dont ask people on an internet forum would be my first suggestion.
Call your Bell or PWC tech rep thats what they are there for.
If its just a personal thing do it without mentioning the company. Most of the tech reps ive dealt with are very helpful.
(15 minutes test flight sounds pretty conclusive though.)
Call your Bell or PWC tech rep thats what they are there for.
If its just a personal thing do it without mentioning the company. Most of the tech reps ive dealt with are very helpful.
(15 minutes test flight sounds pretty conclusive though.)
15 minute test flight sounds a bit silly to me, especially if part of the cover was missing!!
Call tech rep first, if you can't find a procedure for suspected FOD injestion.
Start with the easy stuff. Remove the mesh grill from the intake and feel for damage on the first stage compressor. Insert borescope down compressor and check further stages, and impeller, if you can.
Remove an ignitor plug and borescope the combustion liner checking for damage. Insert the borescope guide into said igniter hole, and check the Nozzle Guide Vane, and Compressor Turbine.
Any damage found, refer PT6T manual for limits. No damage found, ITT was in limits, compressor didn't surge, then all should be OK.
Spanish Waltzer, if you don't trust your engineers, maybe you should change jobs. They undergo 10,000 hours of practical and theory training just to get a basic licence, then extra requirements for each type rating on top.
Call Agusta (there should be a P&W rep there), or call P&W direct. They should be able to help. And pleeeeeaaassssseeee tell them EVERYTHING. I have been involved in fault finding where the pilot didn't want to tell us everything because he thought he would look silly. After 5 days trying to trace and replicate the fault, we finally got the whole story, and went straight to the problem.
Apart from the 15 minute trest flight, I agree with tuk tuk boom boom.
Regards
Call tech rep first, if you can't find a procedure for suspected FOD injestion.
Start with the easy stuff. Remove the mesh grill from the intake and feel for damage on the first stage compressor. Insert borescope down compressor and check further stages, and impeller, if you can.
Remove an ignitor plug and borescope the combustion liner checking for damage. Insert the borescope guide into said igniter hole, and check the Nozzle Guide Vane, and Compressor Turbine.
Any damage found, refer PT6T manual for limits. No damage found, ITT was in limits, compressor didn't surge, then all should be OK.
Spanish Waltzer, if you don't trust your engineers, maybe you should change jobs. They undergo 10,000 hours of practical and theory training just to get a basic licence, then extra requirements for each type rating on top.
Call Agusta (there should be a P&W rep there), or call P&W direct. They should be able to help. And pleeeeeaaassssseeee tell them EVERYTHING. I have been involved in fault finding where the pilot didn't want to tell us everything because he thought he would look silly. After 5 days trying to trace and replicate the fault, we finally got the whole story, and went straight to the problem.
Apart from the 15 minute trest flight, I agree with tuk tuk boom boom.
Regards