Few interview q's
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Few interview q's
Got my interview later this week and have a couple of questions for anyone that might be able to help.
What leading edge devices does the B744, B777, A330 and A340 have?
Why do you have to set EPR by 80 knots?
Why don't you retract undercarriage when executing a missed approach if you encountered windshear?
If you have a pitot tube blockage, does it affect both captains and co-pilots instruments, or are they taking information from different sources?
What leading edge devices does the B744, B777, A330 and A340 have?
Why do you have to set EPR by 80 knots?
Why don't you retract undercarriage when executing a missed approach if you encountered windshear?
If you have a pitot tube blockage, does it affect both captains and co-pilots instruments, or are they taking information from different sources?
Last edited by 100% Ng; 22nd Aug 2005 at 01:37.
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1. They dont have leading edge flaps, they have slats, with slots. (see here for more: http://142.26.194.131/aerodynamics1/...ge5.html#plain)
2. EPR is the ratio of the air pressure enters the engine vs that behind the fan (P5 vs P2). As you accel down the runway the pressure entering increases....giving a 'false' decrease in EPR. (known as ram rise) Power checks before 80kts are still considered effective.
3. a. Impact protection b. Gear doors are huge. Raising the gear, opens the doors, and increases drag...just when you dont want too!
4. Capt, FO and Stby instruments all have their own pitot and static sources.
Ed, for por speling
2. EPR is the ratio of the air pressure enters the engine vs that behind the fan (P5 vs P2). As you accel down the runway the pressure entering increases....giving a 'false' decrease in EPR. (known as ram rise) Power checks before 80kts are still considered effective.
3. a. Impact protection b. Gear doors are huge. Raising the gear, opens the doors, and increases drag...just when you dont want too!
4. Capt, FO and Stby instruments all have their own pitot and static sources.
Ed, for por speling
Last edited by petitfromage; 23rd Aug 2005 at 03:35.
Actually,
1)I'm pretty sure you'll find the 744 has Krueger Flaps. Not sure about the Airbii
2)EPR is the ratio of Jet Pipe Pressure (P7) to Compressor Inlet Pressure (P2). As you accelerate down the runway there is a "Ram Rise" causing the P2 pressure to rise, which in turn lowers the EPR reading. You want it set by 80kts so you don't end up spending the whole take off run messing with the thrust levers.
There is a pretty good thread somewhere on Pprune about this.
Make sure you also understand Integrated EPR which is used on Fan Engines. It's the ratio of integrated turbine discharge and fan outlet pressure to compressor inlet pressure. I was asked about this on my interview.
petitfromage hit the nail on the with regards to the gear. On the 744, when the gear is down, the doors are retracted. When you raise the gear the doors come down, creating a huge amount of drag.
Ditto with the pitot static sources. I'm pretty sure most modern jet aircraft have at least 3 independent P/S sources. Some might have another, not sure.
petitfromage, wasn't trying to have a pi$$ing match, just wanted to steer our fellow ppruner in the right direction.
PS, make sure you have thought about what you would do if it's not your company proceedure to put the TPXDR to TA from TA/RA and you lose an engine and then subsequently get an RA.
100% Ng, good luck and let us know how you do.
1)I'm pretty sure you'll find the 744 has Krueger Flaps. Not sure about the Airbii
2)EPR is the ratio of Jet Pipe Pressure (P7) to Compressor Inlet Pressure (P2). As you accelerate down the runway there is a "Ram Rise" causing the P2 pressure to rise, which in turn lowers the EPR reading. You want it set by 80kts so you don't end up spending the whole take off run messing with the thrust levers.
There is a pretty good thread somewhere on Pprune about this.
Make sure you also understand Integrated EPR which is used on Fan Engines. It's the ratio of integrated turbine discharge and fan outlet pressure to compressor inlet pressure. I was asked about this on my interview.
petitfromage hit the nail on the with regards to the gear. On the 744, when the gear is down, the doors are retracted. When you raise the gear the doors come down, creating a huge amount of drag.
Ditto with the pitot static sources. I'm pretty sure most modern jet aircraft have at least 3 independent P/S sources. Some might have another, not sure.
petitfromage, wasn't trying to have a pi$$ing match, just wanted to steer our fellow ppruner in the right direction.
PS, make sure you have thought about what you would do if it's not your company proceedure to put the TPXDR to TA from TA/RA and you lose an engine and then subsequently get an RA.
100% Ng, good luck and let us know how you do.
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Indeed, sorry for the bum steer; the 747 definitely has kruger flaps viewed here: http://www.airliners.net/open.file?i...bl=TAIL&size=L
The 777 & Airbus' are all slats/slots.
The 777 & Airbus' are all slats/slots.
Guys,
The whole EPR increase/decrease thing was driving me nuts because some were saying it increased and some were saying that it decreaesed.
I think the confusion arises becauses N1 will increase on the TO roll due to Ram Rise. However EPR is a ratio of what comes out to what goes in. (extremely simplified). So if the pressure at the front incrases due to Ram Rise but the pressure out the back stays the same or doesn't increase as much, the overall ratio is lower.
I couldn't get a straight answer but I get to work by jumpseating on the A320, more often than not and I watched the EPR gauges. They did indeed show a decrease.
If I'm wrong I will be more than happy to buy the 1st round.
The whole EPR increase/decrease thing was driving me nuts because some were saying it increased and some were saying that it decreaesed.
I think the confusion arises becauses N1 will increase on the TO roll due to Ram Rise. However EPR is a ratio of what comes out to what goes in. (extremely simplified). So if the pressure at the front incrases due to Ram Rise but the pressure out the back stays the same or doesn't increase as much, the overall ratio is lower.
I couldn't get a straight answer but I get to work by jumpseating on the A320, more often than not and I watched the EPR gauges. They did indeed show a decrease.
If I'm wrong I will be more than happy to buy the 1st round.
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I have been told by an engineer that the B744 does NOT have "true" kruger flaps. Something to do with the linkages. They have Variable Camber Slats. Module 1 (outboard the engines) and Module 2 (between engines) are VCS. Module 3 (between engine and fuselage) are “kruger” flaps, but not real kruger flaps if you understand. 
Kenny, you are correct. The EPR value does decrease as the ram effect increases intake pressure. Another reason to have EPR set by 80 knots is that if you don't, your performance calculations are invalid. The ususal procedure if it isn't set by then is to set TOGA power.
The 747 has three groups of leading edge flaps. The inboards are indeed Kruger flaps. The two outboard groups are variable camber flaps which are composite panels which are flat when stowed but bend into shape when deployed.
The 747 has three groups of leading edge flaps. The inboards are indeed Kruger flaps. The two outboard groups are variable camber flaps which are composite panels which are flat when stowed but bend into shape when deployed.
