Hi folks, 

 

I am just cruising back from MHTG, Toncontin to CYYZ, Toronto Pearson Int'l

at FL370, heading for Varadero UVA VOR, TAT -17°C, SAT -45°C,  

and I wanted to check on when I have to service my Westjet 737-600 Whiskey Sierra. (Answer: 89hours). 

 

Doing this I saw that there is an active failure: LEFT BLEED DUCT LEAK. 

 

Huh, a quick glance into the QRH reveals that I am doomed for a WING BODY OVERHEAT, 

which is *not* yet illuminated. 

 

So, my skeak preview was of course not realistic. 

How could I detect a BLEED DUCT LEAK *before* the WING BODY OVERHEAT comes on? 

 

Thanx in advance. 

Im not sure, do you notice a difference between the L and R Duct pressure gauge?

 

Im not sure, do you notice a difference between the L and R Duct pressure gauge?

There can be quite a big PSID (<20PSI) under normal situations RW. I'm not sure if you could judge by that or not.

do you notice a difference between the L and R Duct pressure gauge?

 

Hi Bryan, 

 

nope, no difference in the gauge pressures L and R. 

 

I de-activated it, and then activated again, both to no avail. 

Does it have an effect on your aircraft? 

 

1901z: Closed the isolation valve... no effect, both read about 38PSI. 

 

2014z: Now at the gate in CYYZ, engine running in idle, again no difference in pressure: about 18PSI L and R. 

 

Please would one of so kind and activate the fault during flight and describe the effect to me? Thanx in advance. 

Edited March 28, 201313 yr by 19AB67

 

There can be quite a big PSID (<20PSI) under normal situations RW. I'm not sure if you could judge by that or not.

 

Well, yes, the difference in duct pressure would be the indication, but why does it not show? 

Maybe look for a rise in EGT. The leak may not be substantial enough to lower duct pressure.

 

Maybe look for a rise in EGT. The leak may not be substantial enough to lower duct pressure.

 

Nope, Jesse, started the engines again, idle, EGT L 379, R 377, usual difference. 

Does it work on your 737s? 

 

Well, yes, the difference in duct pressure would be the indication, but why does it not show?

I imagine the bleed valve would simply open more to keep the pressure up. You might get an EGT bump since you're now diverting some air. You might simply have to wait for the Caution light.

I imagine the bleed valve would simply open more to keep the pressure up. You might get an EGT bump since you're now diverting some air. You might simply have to wait for the Caution light.

 I did some testing and it seems the NGX does not simulate the relationship between bleed air and engine performance. Now bear with me because I am more a turbo-prop guy than a turbo-fan guy. Opening the bleed air valve reduces the performance of the compressor section of the engine. To compensate, the engine demands more fuel to maintain the desired power setting. This should result in an increase in EGT and possibly N2. N1 should stay the same because that is what the engine is trying to maintain. In a real life scenario, a bleed air leak is a major failure. Bleed air has a temperature up to 600 degrees F and can be very destructive to the air frame. Because of this, the  WING BODY OVERHEAT light should come on almost immediately if you have a bleed air leak. I activated this same failure and let the engines run at climb power for ten minutes and the light never came on. This leads me to believe that bleed air is NOT simulated in NGX. Opening the valves will cause an increase in the duct pressure but thats it. I hope this helps and if anyone else has expanding info please help out.

Well, yes, the difference in duct pressure would be the indication, but why does it not show?

I'll try to answer this question more clearly :rolleyes:. You will only see a loss of duct pressure, assuming the isolation valve is closed, if the engine cannot supply the extra demand. For example, if the ducting completely separated, the pressure indicator would would read 0 or very low depending where the separation was. If this were to happen there would be a fire almost immediately and you would have other problems. If there was a small leak in the ducting somewhere it would not be reflected in the ducting indication. It would be reflected in the engine indication in the form of rising EGT as the bleed air valves try to maintain pressure.  Only if the 5th and 9th stage bleed air valves are completely open and you still cannot maintain pressure, you will see a decrease in duct pressure.