Question for Metro Pilots

[uwochris]

Hey guys,

I have a few questions for anyone who currently flies a metro. I've received different and conflicting answers from fellow pilots, and I was hoping for added input.

1. In my groundschool manual (electrical systems chapter, DC voltmeter switch), it states..... "to read the output of the selected generator or battery, the corresponding battery or generator must be in the OFF position. If left ON, the voltmeter will read DC Bus voltage." I don't quite understand this. Does this mean that if I want to read the voltage of the left generator in flight, I would actually have to turn the left gen OFF?

2. Do you know what the 3 CBs in the wheel well are for? I believe one is the CB for the Generator output sense relay, the 2nd is the CB for the ground fault sensing relay, and the 3rd is the CB for the Gen relay. There is also a 4th CB on the opposite side, which I believe is the CB for the voltmeter.

3. I do not understand the purpose of the "Reset" position for the battery and generator switches. The manual explains it acts to "prime" the generator. I dont see how this works.

4. There are 4 static ports on the nose. I know they are all for the pressurization system, but what exactly is each one for? I know 1 is for the 7.25 PSI relief valve for dump valve,.

5. If the trim system fails, you apparently will get a heavy nose up pitch. Why is this?

If anyone can shed some light on any of these questions, I'd greatly appreciate it. Thanks a lot.

 

[Say Again Over]

Your meter is measuring from the source, such as the L/H battery, unless you remove it from the bus you would possibly be reading GEN voltage of 28.5 instead of battery voltage of 24.5.

 

[ksu_aviator]

These are hard to answer with out looking at a diagram, but I'll do my best.

1. The voltage sensors are located between the source (i.e. gen or batt) and the relay. If the relay is open, you get a true voltage reading, if it is closed, the other sources will contribute to that reading.

2. The CB's in the wheel well are the Gen Control CB's on the Gen Cont Panel. Paralleling and reverse-current protection is on one CB, overvoltage on another, relay control on the third, ground fault on the fourth. Page 2-5 if you have the FSI book.

3. The reset button is for the ground fault protection. If you have the Flight Safety manual it is on page 2-4 on the bottom right. The reason you "Reset" before turning on a battery or generator is to ensure that the ground fault did not trip during shutdown. If the ground fault had tripped and you tried to turn on a gen or batt with out resetting, you would get the amber CAS and the gen or batt would not come on line. If the ground fault had tripped and you reset, assuming the fault was not real, prior to turning on a gen or batt, you will have a normal indication.

4. Pressure Differential, Automatic Cabin Alt Control, Cabin Altitude Warning and possibly the Standby Static (but I'm not sure about the last).

5. Is a new one on me. My understanding is that the the stab trim can fail in any position or it can run away to either up or down. Take a look at the Emergency Procedures in the AFM and that will help you to understand what is happening.