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munirabbasi

NTS Failure

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Hello hercules Flyer expertises

When NTS  malfunction  during hercules bird steep or rapid descending particularly outboard engine what happened with bird? Bird will yah or not, hercules bird fan pitch lock or not? 

Regards

Munir Abbasi

Home of Hercules Pakistan

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High speed anything in the Herc is rare BUT in the case of dives there is the ability to have an increase in airflow through the prop which could cause NTS. This could happen with the throttle at flight idle power off or with power on at any setting above flight idle.  

As the airflow increase the prop wants to drive the engine as the air becomes the drive force not the engine power.

 

IF the NTS fails to increase the blade angle drag will be induced; an outboard prop will have more yaw effect than an inboard prop.    

Would the prop pitchlock is a dynamic question and is dependent on the situation but in reality pitchlock prevents the prop from decreasing blade angle therefore again in theory the blade should continue to increase blade angle.

 

ANYONE have the OLD 1960s "PROPORGANDA" illustrated little book that had all the little "engineers" and "mechanics" drawn in? There are some good explanations on this and other prop engine related topics.

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21 minutes ago, NATOPS1 said:

High speed anything in the Herc is rare BUT in the case of dives there is the ability to have an increase in airflow through the prop which could cause NTS. This could happen with the throttle at flight idle power off or with power on at any setting above flight idle.  

As the airflow increase the prop wants to drive the engine as the air becomes the drive force not the engine power.

 

IF the NTS fails to increase the blade angle drag will be induced; an outboard prop will have more yaw effect than an inboard prop.    

Would the prop pitchlock is a dynamic question and is dependent on the situation but in reality pitchlock prevents the prop from decreasing blade angle therefore again in theory the blade should continue to increase blade angle.

 

ANYONE have the OLD 1960s "PROPORGANDA" illustrated little book that had all the little "engineers" and "mechanics" drawn in? There are some good explanations on this and other prop engine related topics.

NTS system works above flight idle, NTS system work when prop try to rotate engine (during descending,gust load,interruption in TD system,and improper governing) when propeller try to rotate engine (negative torque ) produce this system increase the blade angle when blade angle increase prop RPM decease  become in governing range RPM.                            If ur NTS system fail during descending & NTS system not increasing blade angle through feathering valve and propeller RPM increases obve the pich lock RPM limit ( above 103.5) then propeller should be pitch lock. U can observed pich lock propeller by moving the throttle forward engine RPM follow the throttle movement & torque will be same its indication of pitch lock. REGARDS

Edited by Ahmer

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You are missing the point on NTS in this condition. "Hi speed" dives are not a normal profile and this condition (NTS induced by hi speed airflow) is very rare especially with power on.

Flight idle descent is common but airspeed is usually limited to prevent NTS (airframe limitations)  We usually see NTS at Flt Idle once we arrive at lower altitudes as the air gets more dense and we add a small amount of power to eliminate the NTS condition.

 

NTS is a DIRECT input to the feather valve and bypasses the normal governor. 

If there is an onset of NTS during a hi speed dive and a failure of the NTS system does not increase blade angle; drag will increase and the aircraft will yaw (original posters question) additionally pitchlock while it could/would come into play if the Rpm INCREASED TO 103.5 it is not a factor because the blade is not trying to decrease and while the normal governor should increase the blade angle to maintain RPM we are discussing failures not normal operations and the feather valve should have already commanded a blade angle increase.

It is important to remember if the NTS continues to increase at aprox -4000 inlb TQ the prop should decouple which would actually be a very bad situation because the increase airflow which caused the NTS would now drive the "pitchlocked" propeller very fast and cause even higher drag.

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Yes if NTS system fail prop RPM will be more then power section at that time propeller RPM cross the limit 103.5 . it should be pitch locked and aircraft will yaw opposite direction. If Negative torque increases limit -6000 torque  RGB Decoupled from power section. Definitely if outer engine is pitch lock and pilot not confirmed  the torque should be more when throttle retarted & aircraft will be yawning opposite direction.we experienced of Pitch lock during NTS system failure during decsanding,Fault is with NTS bracket which not properly actuate NTS system.

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1 hour ago, NATOPS1 said:

You are missing the point on NTS in this condition. "Hi speed" dives are not a normal profile and this condition (NTS induced by hi speed airflow) is very rare especially with power on.

Flight idle descent is common but airspeed is usually limited to prevent NTS (airframe limitations)  We usually see NTS at Flt Idle once we arrive at lower altitudes as the air gets more dense and we add a small amount of power to eliminate the NTS condition.

 

NTS is a DIRECT input to the feather valve and bypasses the normal governor. 

If there is an onset of NTS during a hi speed dive and a failure of the NTS system does not increase blade angle; drag will increase and the aircraft will yaw (original posters question) additionally pitchlock while it could/would come into play if the Rpm INCREASED TO 103.5 it is not a factor because the blade is not trying to decrease and while the normal governor should increase the blade angle to maintain RPM we are discussing failures not normal operations and the feather valve should have already commanded a blade angle increase.

It is important to remember if the NTS continues to increase at aprox -4000 inlb TQ the prop should decouple which would actually be a very bad situation because the increase airflow which caused the NTS would now drive the "pitchlocked" propeller very fast and cause even higher drag.

Thanks

Munir Abbasi

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3 hours ago, NATOPS1 said:

High speed anything in the Herc is rare BUT in the case of dives there is the ability to have an increase in airflow through the prop which could cause NTS. This could happen with the throttle at flight idle power off or with power on at any setting above flight idle.  

As the airflow increase the prop wants to drive the engine as the air becomes the drive force not the engine power.

 

IF the NTS fails to increase the blade angle drag will be induced; an outboard prop will have more yaw effect than an inboard prop.    

Would the prop pitchlock is a dynamic question and is dependent on the situation but in reality pitchlock prevents the prop from decreasing blade angle therefore again in theory the blade should continue to increase blade angle.

 

ANYONE have the OLD 1960s "PROPORGANDA" illustrated little book that had all the little "engineers" and "mechanics" drawn in? There are some good explanations on this and other prop engine related topics.

Thanks

Munir Abbasi

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