What are the vents ubder the engines?

[BernieFlyer 2]

I noticed that I have open vents (like cowl flaps) under the Kingair engines. I cannot work out what I have done to open them. Any ideas?

 

Thanks

 

Bernie

[pete_auau 1,154]

They are used  to  cool the engines on take off, some  where  on your  engines  control panel  there will  2  switches  to open and  close   refer   to your manual  that  came  with  your aircraft  since  it  will explain it better

[BernieFlyer 2]

Thanks Pete but none of the manuals I have refer to the engine panel controls. I will continue my search.

[BernieFlyer 2]

Ah ha, I found it. It is the Engine Anti Ice switches that when on open the cowl/vent. Wow, that took a while.

[KenG 492]

 

 

Actually there are two sets of bypass doors on the King Air 200 lower nacelle. The first set as has been stated is the Engine Ice Vane bypass doors, the actual ice vanes are inside the nacelles. Those bypass doors have nothing to do with cooling the engine and are used to change the flow of air causing a sharper angle prior to entering the engine. Thus heavier ice particles will tend to flow out of the engine nacelles while air molecules will still flow into the engine inlet. However, this system (without the Raisbeck Ram Air recovery system) causes performance to be robbed from the engines and with the ice vanes out you will experience less torque and higher ITT for a given N1 setting. Generally the ice vanes are extended below 15 degrees Celsius and in visible moister however can be used above 15 degrees for particle separation, such as a sand storm in the desert. When used above 15 degrees the crew needs to carefully watch oil temperature. 

 

The second set of doors are the bypass doors for the oil cooler. I am not sure if Carenado even models these doors, but they open and close automatically based on thermocouples. As oil is returned from the reduction gear box it goes through a scavenge pump then to a thermocouple that determines if the oil is above a specified temperature. If the oil is above that temperature then the oil is routed to the oil cooler which sits on the engine seal between the inlet section and the accessory section of the engine. Air not used by the engine flows over an air to oil heat exchanger (radiator) that will cause the oil to cool. The bypass door on the bottom of the nacelle behind the ice vane bypass door controls the flow of air across this exchanger and is also opened and closed automatically by a termocouple.

 

Since the ice vane bypass door sits prior to the oil cooler when you use the ice vanes you also rob air from the oil cooler which is why you have to watch engine oil when using the system above 15 degrees. (Except on later King Air 200s and King Air 250s that were redesigned with the pitot inlet. As part of the nacelle redesign they also moved the oil cooler. Same thing on King Air 300/350s and later 90s.)

 

 

 

[BernieFlyer 2]

Wow, thanks for such a detailed and interesting response. One keeps learning!!