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virage
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Strange probes on the A350

Sat Feb 08, 2020 5:56 am

What are the probes or antennae behind the main gear as seen on the following photo?
They don't appear on any of the A350's I've seen before.
 
unimproved
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Re: Strange probes on the A350

Sat Feb 08, 2020 6:16 am

That's a deployed RAT. The A330 has it under the wing.

https://www.airliners.net/photo/Hainan- ... 43/1332359
 
virage
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Re: Strange probes on the A350

Sat Feb 08, 2020 6:17 am

unimproved wrote:
That's a deployed RAT. The A330 has it under the wing.

https://www.airliners.net/photo/Hainan- ... 43/1332359


Thanks! It's an unusual location for RAT. They're typically located in the tail or under the wing, as in your A330 example.
 
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fr8mech
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Re: Strange probes on the A350

Sat Feb 08, 2020 6:57 am

virage wrote:
Thanks! It's an unusual location for RAT. They're typically located in the tail or under the wing, as in your A330 example.


B757/B767 has them aft of the gear. What aircraft has the RAT installed in the tail?
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Francoflier
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Re: Strange probes on the A350

Sat Feb 08, 2020 9:43 am

The A350 has it in the exact same location as the 777.
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rjsampson
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Re: Strange probes on the A350

Sun Feb 09, 2020 5:12 pm

I've never seen a RAT test. Just how loud is it? Audible within the cabin/cockpit? From an observer perspective: Would the RAT be the loudest noice emanating on a landing? And while I'm sure this varies by Type, airspeed, etc: What kind of RPM are we talking? Is the RPM governed to an upper-limit?
"..your eyes will be forever turned skyward, for there.." yeah we know the DaVinci quote. Unfortunately, we're grounded :(
 
Dalmd88
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Re: Strange probes on the A350

Sun Feb 09, 2020 11:50 pm

rjsampson wrote:
I've never seen a RAT test. Just how loud is it? Audible within the cabin/cockpit? From an observer perspective: Would the RAT be the loudest noice emanating on a landing? And while I'm sure this varies by Type, airspeed, etc: What kind of RPM are we talking? Is the RPM governed to an upper-limit?

The hangar tests are possible the most annoying test I've ever heard on an airplane, especially the Airbus A320. In the old Delta four bay narrow body hangar the sound was deafening. You hook up a special hydraulic cart to back drive it to the proper RPM and then measure the output of the electrical generator. I can't recall the RPM, I only did the test myself like once and it was years ago.
 
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rjsampson
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Re: Strange probes on the A350

Mon Feb 10, 2020 1:20 am

Dalmd88 wrote:
The hangar tests are possible the most annoying test I've ever heard on an airplane, especially the Airbus A320. In the old Delta four bay narrow body hangar the sound was deafening.


Maddog, thank you so much for your response. TechOps at ATL? That sounds like it must’ve been “fun!” Just found a 77 RAT hangar test on YT. No doubt the volume isn’t sufficiently captured but it sounds as unpleasant as you described: https://shorturl.at/xzGH3

Can anyone speak to my aforementioned questions on airliners? (Noise inside and out, RPM, whether it’s governed, etc)?
"..your eyes will be forever turned skyward, for there.." yeah we know the DaVinci quote. Unfortunately, we're grounded :(
 
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Starlionblue
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Re: Strange probes on the A350

Mon Feb 10, 2020 2:48 am

rjsampson wrote:
Dalmd88 wrote:
The hangar tests are possible the most annoying test I've ever heard on an airplane, especially the Airbus A320. In the old Delta four bay narrow body hangar the sound was deafening.


Maddog, thank you so much for your response. TechOps at ATL? That sounds like it must’ve been “fun!” Just found a 77 RAT hangar test on YT. No doubt the volume isn’t sufficiently captured but it sounds as unpleasant as you described: https://shorturl.at/xzGH3

Can anyone speak to my aforementioned questions on airliners? (Noise inside and out, RPM, whether it’s governed, etc)?


Unfortunately, my manuals don't have much beyond "powered by the RAT" plus the fact that mininum RAT speed is 140 knots. I guess we don't need to know. :D
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
milhaus
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Re: Strange probes on the A350

Mon Feb 10, 2020 11:22 am

A320 RAT has operating speed 4750RPM when A/C speed is 92-135KT, when speed is lower antistall systems adjusts output of the hyd pumps in balance to the speed of turbine.
 
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tjwgrr
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Re: Strange probes on the A350

Mon Feb 10, 2020 7:31 pm

rjsampson wrote:
Maddog, thank you so much for your response. TechOps at ATL? That sounds like it must’ve been “fun!” Just found a 77 RAT hangar test on YT. No doubt the volume isn’t sufficiently captured but it sounds as unpleasant as you described: https://shorturl.at/xzGH3

Can anyone speak to my aforementioned questions on airliners? (Noise inside and out, RPM, whether it’s governed, etc)?


Is the RAT what we're hearing on this video when DL 89 was dumping fuel?
https://www.youtube.com/watch?v=zIrFNADfnj8
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unimproved
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Re: Strange probes on the A350

Mon Feb 10, 2020 9:50 pm

rjsampson wrote:
Dalmd88 wrote:
The hangar tests are possible the most annoying test I've ever heard on an airplane, especially the Airbus A320. In the old Delta four bay narrow body hangar the sound was deafening.


Maddog, thank you so much for your response. TechOps at ATL? That sounds like it must’ve been “fun!” Just found a 77 RAT hangar test on YT. No doubt the volume isn’t sufficiently captured but it sounds as unpleasant as you described: https://shorturl.at/xzGH3

Can anyone speak to my aforementioned questions on airliners? (Noise inside and out, RPM, whether it’s governed, etc)?

Indeed, much worse than just cranking an engine

It also blows away anything in its path, lovely when working on the aft cargo door
 
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Starlionblue
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Re: Strange probes on the A350

Tue Feb 11, 2020 2:31 am

tjwgrr wrote:
rjsampson wrote:
Maddog, thank you so much for your response. TechOps at ATL? That sounds like it must’ve been “fun!” Just found a 77 RAT hangar test on YT. No doubt the volume isn’t sufficiently captured but it sounds as unpleasant as you described: https://shorturl.at/xzGH3

Can anyone speak to my aforementioned questions on airliners? (Noise inside and out, RPM, whether it’s governed, etc)?


Is the RAT what we're hearing on this video when DL 89 was dumping fuel?
https://www.youtube.com/watch?v=zIrFNADfnj8


They wouldn't have needed the RAT. I think what you're hearing is a helicopter or something.
"There are no stupid questions, but there are a lot of inquisitive idiots." - John Ringo
 
OldAeroGuy
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Re: Strange probes on the A350

Tue Feb 11, 2020 6:56 pm

rjsampson wrote:
I've never seen a RAT test. Just how loud is it? Audible within the cabin/cockpit? From an observer perspective: Would the RAT be the loudest noice emanating on a landing? And while I'm sure this varies by Type, airspeed, etc: What kind of RPM are we talking? Is the RPM governed to an upper-limit?


My nearly 40yo recollection from 757 testing is that for cruise conditions, the RAT sounded a lot like a Piper Cub at full power had been strapped to the fuselage.

The 757/767 RATs use blade pitch control to limit max RPM to around 5000 RPM (i think). Blade pitch RPM governors are standard for all RATs I've been associated with.

If you observe Boeing production flight tests at Paine Field, you'll get to see many deployed RATs. RAT deployment is standard for B1 flight tests on all 747-8, 767, 777 and 787 models.
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Horstroad
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Re: Strange probes on the A350

Tue Feb 11, 2020 11:34 pm

rjsampson wrote:
What kind of RPM are we talking? Is the RPM governed to an upper-limit?

On the 777 the rat is governed by flyweights to 4510 rpm. It is a 41.5" two-bladed turbine which produces 7.5 KVA 115v ac and 2850 psi hydraulic pressure with a flow rate of 10 gpm.

The test of the MD11 rat is the loudest I've experienced so far. It doesn't produce hydraulic pressure, only electricity. So to test it you have to generate air speed. This is done by hooking two air start units to a venturi jet pump which adds to the noise of the rat itself. This test is always done outside of the hangar.
 
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rjsampson
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Re: Strange probes on the A350

Wed Feb 12, 2020 2:17 am

Starlionblue wrote:
tjwgrr wrote:
Is the RAT what we're hearing on this video when DL 89 was dumping fuel?
https://www.youtube.com/watch?v=zIrFNADfnj8


They wouldn't have needed the RAT. I think what you're hearing is a helicopter or something.


Yeah, that was my initial thought (and that of pretty much everyone else, responding to people that initially suggested that it could have been the RAT)

....then again: It would seem that this crew weren't exactly following best practices by opening the dumps on Final. Could they have manually deployed the RAT? I still don't think that's what it was but: Man: The doppler sound of (whatever it was) perfectly matches up with their flight path. Like: perfectly.
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Starlionblue
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Re: Strange probes on the A350

Wed Feb 12, 2020 2:24 am

rjsampson wrote:
Starlionblue wrote:
tjwgrr wrote:
Is the RAT what we're hearing on this video when DL 89 was dumping fuel?
https://www.youtube.com/watch?v=zIrFNADfnj8


They wouldn't have needed the RAT. I think what you're hearing is a helicopter or something.


Yeah, that was my initial thought (and that of pretty much everyone else, responding to people that initially suggested that it could have been the RAT)

....then again: It would seem that this crew weren't exactly following best practices by opening the dumps on Final. Could they have manually deployed the RAT? I still don't think that's what it was but: Man: The doppler sound of (whatever it was) perfectly matches up with their flight path. Like: perfectly.


I guess. But it's not really something you would do by accident. The pushbutton/switch would be guarded.
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ro1960
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Re: Strange probes on the A350

Thu Feb 13, 2020 7:02 am

rjsampson wrote:
I've never seen a RAT test. Just how loud is it? Audible within the cabin/cockpit? From an observer perspective: Would the RAT be the loudest noice emanating on a landing?


Here’s a video of the 787 RAT test. It sounds loud but I doubt it will be louder than the engine noise. Plus upon landing, the reduced speed will make it slow down and stop I imagine.

https://youtu.be/O1r3CuRwjPc
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CALTECH
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Re: Strange probes on the A350

Thu Feb 13, 2020 5:06 pm

tjwgrr wrote:
rjsampson wrote:
Maddog, thank you so much for your response. TechOps at ATL? That sounds like it must’ve been “fun!” Just found a 77 RAT hangar test on YT. No doubt the volume isn’t sufficiently captured but it sounds as unpleasant as you described: https://shorturl.at/xzGH3

Can anyone speak to my aforementioned questions on airliners? (Noise inside and out, RPM, whether it’s governed, etc)?


Is the RAT what we're hearing on this video when DL 89 was dumping fuel?
https://www.youtube.com/watch?v=zIrFNADfnj8


No. That was a GA plane with a recip engine flying by.

https://www.youtube.com/watch?v=JaW6gcNk4tw
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BravoOne
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Re: Strange probes on the A350

Thu Feb 13, 2020 7:02 pm

The RAT as installed on the 777 produces both Had and ELC power with Hyd taking precedent over the Elec via load shed. When it's deployed you can hear and feel a hum for the lack of a better word. DL89 did not deploy the RAT, so that is not what you think you were hearing. There are a number of situations that will auto deploy the RAT, or you can manually deploy it. I can't think of a non normal checklist that calls for a manual deployment? Loss of both engines and their respective electrical busses will cause it to auto deploy.
 
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Starlionblue
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Re: Strange probes on the A350

Fri Feb 14, 2020 12:30 am

BravoOne wrote:
The RAT as installed on the 777 produces both Had and ELC power with Hyd taking precedent over the Elec via load shed. When it's deployed you can hear and feel a hum for the lack of a better word. DL89 did not deploy the RAT, so that is not what you think you were hearing. There are a number of situations that will auto deploy the RAT, or you can manually deploy it. I can't think of a non normal checklist that calls for a manual deployment? Loss of both engines and their respective electrical busses will cause it to auto deploy.


On the A330 and A350 manual deployment is the first step of the ALL ENG FAIL checklist. Just in case auto-deployment didn't work.
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