Fan Blade Tips bended forward
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Fan Blade Tips bended forward
Hi, guys.
Maybe someone could shedsome light on it.
I am an aircraft and powerplant mechanic but working as a Pilot since 15 years and so far a bit rusty on my mechanic skills.
We in our company operating Bombardier Challengers 604 and 605 with the CF34-3B Engines.
We just had it a 3rd time in the last 7 years that on take off in icing conditions the fan blades tips bended forward on one or both engines. All operation has been done according the limitations and the AFM. So Anti Ice has been selected on for take off.
Normaly everything should have been ok. So why are the Blades get bended forward? This time we had to change 10 Blades.
Plus it is not that it happend to 3 or 4 blades in a row. There is one than 2 or 3 are ok and then its another one affected.
Thank you very much for your input.
Bombardier is not very helpful with this as it looks like they dont want to give out any numbers how often this happens to other operators.
Peter
Maybe someone could shedsome light on it.
I am an aircraft and powerplant mechanic but working as a Pilot since 15 years and so far a bit rusty on my mechanic skills.
We in our company operating Bombardier Challengers 604 and 605 with the CF34-3B Engines.
We just had it a 3rd time in the last 7 years that on take off in icing conditions the fan blades tips bended forward on one or both engines. All operation has been done according the limitations and the AFM. So Anti Ice has been selected on for take off.
Normaly everything should have been ok. So why are the Blades get bended forward? This time we had to change 10 Blades.
Plus it is not that it happend to 3 or 4 blades in a row. There is one than 2 or 3 are ok and then its another one affected.
Thank you very much for your input.
Bombardier is not very helpful with this as it looks like they dont want to give out any numbers how often this happens to other operators.
Peter
Solid piece of ice come off somewhere forward of the intake...
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I should image it is like a prop, a prop under power bends forward because the prop forms a forward cone, and on impact the blade simply bends that direction otherwise it would have to lift the aircraft physically up off the ground to allow it to bend backwards. Either that or did it surge? I also wonder if the ice going through has hit the rear of the blade or the leading edge and with the cone effect that caused it.
Last edited by NutLoose; 17th Nov 2016 at 11:42.
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Hi, the aircraft has been de-iced and the wings and the engine inlet has been cleaned or clean.
So no ice in the vicinity where it could probably hit the engines.
Found a while ago a power point presentation about different fan blade damages and their prossible cause.
With the tips bended forward they where refering as a possible too low power setting during approach in icing conditions where ice could form on the back side of the fan blades. This might cause, when changing the power later during approach or when setting reverse power to twist and or bend the blades forward.
Dont know if I am allowed to post this power point slides here on the forum.
This is exactly the wording at least what they said. Same pictures as mine :
Only two fan blades damaged
The blade tip curls are smooth with no obvious impact deformation
The energy of the impact did not result in blade tearing
FAST samples revealed no foreign debris
This is consistent with ice damage
The ice ingestion occurred during a low power setting, probably during the approach phase
The scratch on one of the fan blades below the tip curl was due to the two blades being shipped together for analysis and not protected from contact with one another
So no ice in the vicinity where it could probably hit the engines.
Found a while ago a power point presentation about different fan blade damages and their prossible cause.
With the tips bended forward they where refering as a possible too low power setting during approach in icing conditions where ice could form on the back side of the fan blades. This might cause, when changing the power later during approach or when setting reverse power to twist and or bend the blades forward.
Dont know if I am allowed to post this power point slides here on the forum.
This is exactly the wording at least what they said. Same pictures as mine :
Only two fan blades damaged
The blade tip curls are smooth with no obvious impact deformation
The energy of the impact did not result in blade tearing
FAST samples revealed no foreign debris
This is consistent with ice damage
The ice ingestion occurred during a low power setting, probably during the approach phase
The scratch on one of the fan blades below the tip curl was due to the two blades being shipped together for analysis and not protected from contact with one another
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Dont worry,
""""""when setting reverse power to twist and or bend the blades forward.""""""
I'm not sure what you mean by this statement. When reverse is selected, the blocker doors deploy and fan flow is directed through the cascade assemblies and outward forward of the fan cowls which have been driven aft by the Power Drive Unit. As you pull up on the piggy-back levers, you simply increase engine speed and airflow; this is not like reverse pitch.
Ice coming off the wing, would bend the blades backward if any; not enough speed and energy to cause this damage.
You mentioned you had de-icing performed before take-off, but the crews are told to stay away from the fans (and the T2 sensor); therefore it is possible to have had ice formation aft of the fan blades; if a piece of ice flew aft, it hit the low pressure compressor blades, it/they got fired back forward with a vengeance, causing your dents and bends.
Have a good look at your compressor blades for nicks...
You also mentioned selecting anti-ice on before take-off, but the blades do not get de-iced by bleed air, only the inlet cowls do.
If you have to be outside during bad weather conditions, you may want to install your engine cover, until ready to start, otherwise you should climb on the wing and look behind the fan for any accumulation...
Someone was asking how the wings are de-iced: the wings by the 10th stage and the cowls by the 14th stage.
Last, have a good look between the fan and the l.p. compressor for any missing hardware...you never know.
""""""when setting reverse power to twist and or bend the blades forward.""""""
I'm not sure what you mean by this statement. When reverse is selected, the blocker doors deploy and fan flow is directed through the cascade assemblies and outward forward of the fan cowls which have been driven aft by the Power Drive Unit. As you pull up on the piggy-back levers, you simply increase engine speed and airflow; this is not like reverse pitch.
Ice coming off the wing, would bend the blades backward if any; not enough speed and energy to cause this damage.
You mentioned you had de-icing performed before take-off, but the crews are told to stay away from the fans (and the T2 sensor); therefore it is possible to have had ice formation aft of the fan blades; if a piece of ice flew aft, it hit the low pressure compressor blades, it/they got fired back forward with a vengeance, causing your dents and bends.
Have a good look at your compressor blades for nicks...
You also mentioned selecting anti-ice on before take-off, but the blades do not get de-iced by bleed air, only the inlet cowls do.
If you have to be outside during bad weather conditions, you may want to install your engine cover, until ready to start, otherwise you should climb on the wing and look behind the fan for any accumulation...
Someone was asking how the wings are de-iced: the wings by the 10th stage and the cowls by the 14th stage.
Last, have a good look between the fan and the l.p. compressor for any missing hardware...you never know.
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Hi, thank you for the help so far.
Its not, that I dont know how the reverse works.
What I ment was concerning the statement on this particular power point presentation, that during a low power setting on approach, ice can form on the fan blades either the forward or the aft side. Then when you land and pull the reverse, you increase the RPM N1 and N2 which is diffent to the low power setting and this might cause the formed ice to detach and then cause the damage.
Right ? Wrong?
Any other guesses
Its not, that I dont know how the reverse works.
What I ment was concerning the statement on this particular power point presentation, that during a low power setting on approach, ice can form on the fan blades either the forward or the aft side. Then when you land and pull the reverse, you increase the RPM N1 and N2 which is diffent to the low power setting and this might cause the formed ice to detach and then cause the damage.
Right ? Wrong?
Any other guesses
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We can agree that for the blades to get damaged like this, it requires hard and fast moving objects coming from behind the fan disc; ice conditions may be the cause, but don't neglect any other possibilities like FOD.
Your GE rep. should be able to assist with this; they have surely seen it before.
Good luck.
Your GE rep. should be able to assist with this; they have surely seen it before.
Good luck.
Fan blade icing, possible on the ground.
Freezing fog ice tends to be migrate towards the tip and /or be shed tangentially where ice from the leading edge of a preceding blade strikes the rear of a following blade directly or after ricocheting from the fan casing.
Some engines have a procedure for on-ground ice shedding requiring a moderate increase in fan speed at set intervals; if not the problem may be encountered during the high power take off settings.
The crew may detect a fan buzz when on the ground.
Any F100 pilots for comment.
Freezing fog ice tends to be migrate towards the tip and /or be shed tangentially where ice from the leading edge of a preceding blade strikes the rear of a following blade directly or after ricocheting from the fan casing.
Some engines have a procedure for on-ground ice shedding requiring a moderate increase in fan speed at set intervals; if not the problem may be encountered during the high power take off settings.
The crew may detect a fan buzz when on the ground.
Any F100 pilots for comment.
I see nothing inconsistent with the 'basic physics' of the situation, when you take into consideration the Angle of Attack of the fan blade.
To do a little experiment... press the corner edge of a stiff card with your finger, it will either bend backwards or forwards, in a random way.
However press the same edge, with the card held at 15 degrees, and it will always bend forward in the direction of this AoA.
.
To do a little experiment... press the corner edge of a stiff card with your finger, it will either bend backwards or forwards, in a random way.
However press the same edge, with the card held at 15 degrees, and it will always bend forward in the direction of this AoA.
.
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Hi Guys,
I've not worked on Bombardiers, but from my experience with Boeing powerplants this damage is fairly consistent with FOD damage.
I'm pretty sure this isn't tip curl. Due to 1) the damage pattern, and 2) the speeds of the N1 spool.
I've not worked on Bombardiers, but from my experience with Boeing powerplants this damage is fairly consistent with FOD damage.
I'm pretty sure this isn't tip curl. Due to 1) the damage pattern, and 2) the speeds of the N1 spool.
