IFMU
June 12, 2025, 22:25:00 GMT
permalink Post: 11899752

Quote:

Originally Posted by bobdxb

Primary trigger: Loss of all four AC power sources.

These include:
- Left Integrated Drive Generator (IDG)
- Right IDG
- Left Backup Generator
- Right Backup Generator
  Engine failure alone does not trigger the RAT, must be all of above

There are no IDGs on a 787. There are 4 identical variable frequency starter-generators.

Subjects Engine Failure (All) Generators/Alternators RAT (All) RAT (Deployment)

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IFMU
June 13, 2025, 17:52:00 GMT
permalink Post: 11900688

Quote:

Originally Posted by tumtiddle

Jump to 1:48 in this video (if the link doesn't automatically put you there): https://youtu.be/SbDJjgN7Xbo?si=ShNJ2oA39j46iw9M&t=108
You can't hear that RAT sound at the very beginning of the flypast?

I've only heard RATs in the wind tunnel, and the sound does not jump out at me as being a RAT.

Subjects RAT (All)

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IFMU
June 14, 2025, 02:03:00 GMT
permalink Post: 11901050

Quote:

Originally Posted by HumbleDeer

That's because the RAT is ultimately either deployed because it's "forced" out by an active signal, OR it's deployed because the electromagnetic system is de-energized and the spring loaded mount flaps it out. That's what happens when nothing is stopping the spring from doing spring action things, like you'd see when there's no power going to whatever usually holds it shut.

The solenoid is powered to deploy the RAT. Otherwise it would deploy when parked with no power. Speaking as an engineer from the factory where they are designed, built, and tested.

Subjects RAT (All) RAT (Deployment)

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IFMU
June 17, 2025, 15:56:00 GMT
permalink Post: 11904373

Quote:

Originally Posted by Icarus2001

Simply that the RAT is an electrical generator, that is all.

The 787 RAT has both a generator and a hydraulic pump.

Subjects Generators/Alternators Hydraulic Failure (All) RAT (All) RAT (Electrical)

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IFMU
June 21, 2025, 14:04:00 GMT
permalink Post: 11907729

Quote:

Originally Posted by jdaley

Another post referenced the RAT only supplying electrical power after 10s - I find that hard to believe, not instant obviously because there has to be some stabilisation time and startup/boot time but it would imply the LH flight instruments would only be active very late. Hopefully the RAT hydraulics would be effective quicker than that.

When we start them in the wind tunnel they are making power very quickly. That's the whole point. The RAT GCU is a simple machine.

Subjects RAT (All)

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IFMU June 12, 2025, 22:25:00 GMT permalink Post: 11899752	Quote: Originally Posted by bobdxb Primary trigger: Loss of all four AC power sources. These include: Left Integrated Drive Generator (IDG) Right IDG Left Backup Generator Right Backup Generator Engine failure alone does not trigger the RAT, must be all of above There are no IDGs on a 787. There are 4 identical variable frequency starter-generators. Subjects Engine Failure (All) Generators/Alternators RAT (All) RAT (Deployment) Links are to this post in the relevant subject page so that this post can be seen in context. The thread is closed so there are no user likes are available and no reply is possible.
IFMU June 13, 2025, 17:52:00 GMT permalink Post: 11900688	Quote: Originally Posted by tumtiddle Jump to 1:48 in this video (if the link doesn't automatically put you there): https://youtu.be/SbDJjgN7Xbo?si=ShNJ2oA39j46iw9M&t=108 You can't hear that RAT sound at the very beginning of the flypast? I've only heard RATs in the wind tunnel, and the sound does not jump out at me as being a RAT. Subjects RAT (All) Links are to this post in the relevant subject page so that this post can be seen in context. The thread is closed so there are no user likes are available and no reply is possible.
IFMU June 14, 2025, 02:03:00 GMT permalink Post: 11901050	Quote: Originally Posted by HumbleDeer That's because the RAT is ultimately either deployed because it's "forced" out by an active signal, OR it's deployed because the electromagnetic system is de-energized and the spring loaded mount flaps it out. That's what happens when nothing is stopping the spring from doing spring action things, like you'd see when there's no power going to whatever usually holds it shut. The solenoid is powered to deploy the RAT. Otherwise it would deploy when parked with no power. Speaking as an engineer from the factory where they are designed, built, and tested. Subjects RAT (All) RAT (Deployment) Links are to this post in the relevant subject page so that this post can be seen in context. The thread is closed so there are no user likes are available and no reply is possible.
IFMU June 17, 2025, 15:56:00 GMT permalink Post: 11904373	Quote: Originally Posted by Icarus2001 Simply that the RAT is an electrical generator, that is all. The 787 RAT has both a generator and a hydraulic pump. Subjects Generators/Alternators Hydraulic Failure (All) RAT (All) RAT (Electrical) Links are to this post in the relevant subject page so that this post can be seen in context. The thread is closed so there are no user likes are available and no reply is possible.
IFMU June 21, 2025, 14:04:00 GMT permalink Post: 11907729	Quote: Originally Posted by jdaley Another post referenced the RAT only supplying electrical power after 10s - I find that hard to believe, not instant obviously because there has to be some stabilisation time and startup/boot time but it would imply the LH flight instruments would only be active very late. Hopefully the RAT hydraulics would be effective quicker than that. When we start them in the wind tunnel they are making power very quickly. That's the whole point. The RAT GCU is a simple machine. Subjects RAT (All) Links are to this post in the relevant subject page so that this post can be seen in context. The thread is closed so there are no user likes are available and no reply is possible.

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