IronManNDFW
Condo Jet Captain
- Joined
- Nov 30, 2001
- Posts
- 84
DYK 025: Beechjet Engine Heat August 24, 2007
Did You Know About Beechjet Engine Heat?
With the increased usage of engine heat in the Beechjet fleet we are beginning to see a higher rate of valve failure for this critical system.
How Do I Tell if My Aircraft has a Problem?
A couple of symptoms points directly to either a complete failure or a partial failure of the engine heat bleed air valves. The easiest way to detect the failure is to turn on the engine heat at altitude and watch the Eng Ice Temp Lo annunciators. If one or both illuminate momentarily and then go out almost immediately, this indicates a possible failure of the engine heat bleed air valves on that engine.
The second way to detect a potential failure of this critical system is to look at the ITT on each engine. An engine with the bleed air valve stuck open or partially open will display a higher ITT than an engine with the bleed air valves closed when the switches are in the off position. However, this is not the preferred method of detecting the issue. By far the easiest and most accurate way of detecting the failure is through observation of the annunciators.
Why is This so Critical?
Because of the rash of dual engine flameouts in Beechjets, Pratt & Whitney has completed extensive research and testing on the JT15D-5 engine. They have determined the most likely cause is high altitude icing behind the fan disk on the fixed stators in the compressor section of the engine. When activated, the engine heat provides heated bleed air to these stators, allowing them to be cleared of ice prior to power reduction at altitude. Unfortunately, the annunciators in the cockpit only provide an indication of the system not heating properly; they do not provide any indication of the system being heated continuously, which can become an issue as the aircraft descends into warm air. Above 10 degrees Celsius, if the bleed air valves remain open you are, by definition, exceeding an aircraft limitation.
Also, if you observe indications that the bleed air valves are not functioning properly, it does not necessarily indicate a failure of the valves in the fully open position. Rather, it could indicate the failure of a valve to close completely. If the valve is not closing completely, how confident can a pilot be that it is opening completely? This could equate to quite the surprise as we move toward fall and winter flying!
What Can I Do?
As with any discrepancy, if you observe the Eng Ice Temp Lo annunciators displaying unusual indications, write it up when and where it is discovered. We have no way of knowing the cause of the issue from cockpit indicators. Additionally, we have been warned by the aircraft manufacturer of the critical nature of this system. Better to have a properly trained and certificated mechanic address the issue than to have to put your no-engine approach and landing training to the test!
Now You Know!
Did You Know About Beechjet Engine Heat?
With the increased usage of engine heat in the Beechjet fleet we are beginning to see a higher rate of valve failure for this critical system.
How Do I Tell if My Aircraft has a Problem?
A couple of symptoms points directly to either a complete failure or a partial failure of the engine heat bleed air valves. The easiest way to detect the failure is to turn on the engine heat at altitude and watch the Eng Ice Temp Lo annunciators. If one or both illuminate momentarily and then go out almost immediately, this indicates a possible failure of the engine heat bleed air valves on that engine.
The second way to detect a potential failure of this critical system is to look at the ITT on each engine. An engine with the bleed air valve stuck open or partially open will display a higher ITT than an engine with the bleed air valves closed when the switches are in the off position. However, this is not the preferred method of detecting the issue. By far the easiest and most accurate way of detecting the failure is through observation of the annunciators.
Why is This so Critical?
Because of the rash of dual engine flameouts in Beechjets, Pratt & Whitney has completed extensive research and testing on the JT15D-5 engine. They have determined the most likely cause is high altitude icing behind the fan disk on the fixed stators in the compressor section of the engine. When activated, the engine heat provides heated bleed air to these stators, allowing them to be cleared of ice prior to power reduction at altitude. Unfortunately, the annunciators in the cockpit only provide an indication of the system not heating properly; they do not provide any indication of the system being heated continuously, which can become an issue as the aircraft descends into warm air. Above 10 degrees Celsius, if the bleed air valves remain open you are, by definition, exceeding an aircraft limitation.
Also, if you observe indications that the bleed air valves are not functioning properly, it does not necessarily indicate a failure of the valves in the fully open position. Rather, it could indicate the failure of a valve to close completely. If the valve is not closing completely, how confident can a pilot be that it is opening completely? This could equate to quite the surprise as we move toward fall and winter flying!
What Can I Do?
As with any discrepancy, if you observe the Eng Ice Temp Lo annunciators displaying unusual indications, write it up when and where it is discovered. We have no way of knowing the cause of the issue from cockpit indicators. Additionally, we have been warned by the aircraft manufacturer of the critical nature of this system. Better to have a properly trained and certificated mechanic address the issue than to have to put your no-engine approach and landing training to the test!
Now You Know!
