What's a TRU?

[coolpilot06]

Saw this on an interview gouge...What is a TRU? (I'm assuming it's some kind of system - but we all know what they say about assumptions ) I tried to google it and ran a search here but couldn't find it. If anybody has any incling it's appreciated. Thanks!

[NC_BE300]

Part of an electrical system on some aircraft.

Transformer
Rectifier
Unit

Converts AC to DC electricity

[viper548]

Converts 115 volt AC to 28 volt DC

[woodreau]

Well to my understanding -
T - Transformer part - steps voltage up or down
R - Rectifier part - converts AC power to DC power

[sopdan]

Let me guess... Piedmont?

[TheFlyingTurkey]

Originally Posted by sopdan

Let me guess... Piedmont?

Sounds like it. But I didn't have to know what a TRU was at the interview.

[sopdan]

My old roommate needed to know it about a year ago for their written.

[N261ND]

Also known as a Triple Diod; at least on the Seminole anyway...

[kellwolf]

I think it's on the Pinnacle written test, too. CRJ has 5. I think the question actually asks how many are on the plane.

[BobDDuck]

Originally Posted by kellwolf

I think it's on the Pinnacle written test, too. CRJ has 5. I think the question actually asks how many are on the plane.

Just the 200. The electric system on the 700 and 900 is different as there are only 4 TRUs

[amorris311]

well my seminole supp says it is a diod. gotta start learning this plane. why cant every plane be a simple as a cessna?

[skidz]

Originally Posted by amorris311

well my seminole supp says it is a diod. gotta start learning this plane. why cant every plane be a simple as a cessna?

diode is used to convert ac to dc...so, it's a part of the transformer.

[Tram]

It's also a toy store..

Toys
R
Us.

[Fly4Pay]

Originally Posted by skidz

diode is used to convert ac to dc...so, it's a part of the transformer.

SO close... it's actually part of the rectifier.

[BobDDuck]

Completely unrelated to this thread, but related to Fly4Pay's company and avatar, CHA was like an Airtran parking lot yesterday. 3 737s and a pair of 717s. You'd almost have thought they had started another hub.

[TheFlyingTurkey]

Originally Posted by skidz

diode is used to convert ac to dc...so, it's a part of the transformer.

I've learned a lot about electricity and electronics in the air conditioning industry, and I find it very interesting.

Transformers step voltage either up or down using a coil wire. A voltage is introduced to the coil, which generates a magnetic field. Another coil next to the first coil passes through the field and voltage is generated in the second coil, with an iron bar between the two coils. Voltages are determined by the number of turns in the coil:



Diodes act like electrical check valves. They only allow current to flow in one direction. Looking at the diode symbol below, the direction of flow is the same as the point of the triangle. When you assemble 4 diodes to form a bridge rectifier you convert A/C to D/C. The curved line represents A/C and the solid/dashed line represents D/C.

[kellwolf]

Originally Posted by BobDDuck

Completely unrelated to this thread, but related to Fly4Pay's company and avatar, CHA was like an Airtran parking lot yesterday. 3 737s and a pair of 717s. You'd almost have thought they had started another hub.

Woah. How? I thought CHA was closed for diverts? At least, that's what I saw in the NOTAMs the other day (and every other time I've flown in there).

As for the -200.....well, I don't fly the -700 or -900, so I wouldn't know about that. Plus, the written test here for the interview is based on the -200 anyway. Why anyone needs to know that stuff BEFORE ground school boggles my mind.

What did they do on the -700/900? Combine two DC buses to one TRU?

[BobDDuck]

I didn't know that about CHA. There were the Trannies plus a Frontier BabyBus and two ASA CRJs. Pretty busy ramp.

They dropped the Service TRU on the 700/900. Also, they are uprated to 120 amps. The really cool thing is that in addition to the DC ties that are the same as the 200 there is a link between ESS TRU 1 and ESS TRU 2 that is upstream of the TRUs. So if you loose power to ESS TRU 2 due to an AC failure you can still power it by the same AC power source as ESS TRU 1.

[GreenDayPilot]

So it's pretty much the opposite of an inverter, right?

[TheFlyingTurkey]

Originally Posted by GreenDayPilot

So it's pretty much the opposite of an inverter, right?

Correct.
An inverter converts D/C to A/C.



The red line above represents D/C, and is converted into A/C which is the full sine wave of the blue line. Remember D/C is direct current, and A/C is alternating current. So when you see a sine wave like the blue line, it is alternating, usually at 60 Hz in the USA. Some countries use 50 Hz.

A simple inverter:


Here the D/C circuit starts where the + symbol is, goes through the transistors, and into the coil. This generates a magnetic field. An iron core separates the D/C coil, from the A/C coil. The A/C coil is energized by the magnetic field and is converted to A/C where it shows output.

It can get pretty complicated when you have 3 phases, and multiple transistors. This is the principle behind variable speed motors, like some home Air conditioning blower motors. You can vary the speed of the motor by changing the frequency of the sine wave. This technology is used in commercial and industrial buildings to control motor speed of pumps and fans, saving money on electricity bills.

[Fly4Pay]

Originally Posted by kellwolf

Woah. How? I thought CHA was closed for diverts? At least, that's what I saw in the NOTAMs the other day (and every other time I've flown in there).

It was, for quite a while. Just re-opened a couple of weeks ago.


And we packed it full last Thurs when a BIG line of TSTMS associated with Humberto rolled through during the busy afternoon-evening hours.

[CameronF]

Originally Posted by TheFlyingTurkey

Correct.
An inverter converts D/C to A/C.



The red line above represents D/C, and is converted into A/C which is the full sine wave of the blue line. Remember D/C is direct current, and A/C is alternating current. So when you see a sine wave like the blue line, it is alternating, usually at 60 Hz in the USA. Some countries use 50 Hz.

A simple inverter:


Here the D/C circuit starts where the + symbol is, goes through the transistors, and into the coil. This generates a magnetic field. An iron core separates the D/C coil, from the A/C coil. The A/C coil is energized by the magnetic field and is converted to A/C where it shows output.

It can get pretty complicated when you have 3 phases, and multiple transistors. This is the principle behind variable speed motors, like some home Air conditioning blower motors. You can vary the speed of the motor by changing the frequency of the sine wave. This technology is used in commercial and industrial buildings to control motor speed of pumps and fans, saving money on electricity bills.

Wow thats pretty complex it seems. How much of that is actually required to be explained in an interview?

[Tuckster]

Are you really expected to know these things on the interview Q & A ??

I feel prety good on the ATP stuff but some of the questions I've seen on the gouges seem to be specific to a particular airplane !!!! I'm considering appling to Pinnacle but guess I need more studying. I heard they have a few questions on RNAV equipment as well.

[MattB]

Not on the QnA at piedmont, but know what an inverter is on the written and then there are several 'TRU' questions on the take home study.

[avi8tor]

A rectifier converts AC to DC (remember rectifier wrecks AC) an inverter converts DC to AC.