Rajesh123
Topic Author
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Engine Windmilling on the Ramp

Sun Apr 16, 2017 1:55 pm

Dears

I was on emirates flight landed at UK. What happened was amazing. After landing, we were out on a field waiting for the bus to arrive. However, I was feeling the pull near the engine fan. Luckily I had a bulky backpack which was probably adding to my weight. And I moved away couple of steps, towards the front of the plane.This is kind of old incident, that happened around 4 years ago.

Can anyone tell me please,
1. is that fan nothing but the engine ?
2. Is the pilot not supposed to switch it off so that people are not pulled towards it
3. Am i thinking too much in that I could have been swallowed in the engine because of the pull.
4. What action should I have taken at that time ?
 
MalevTU134
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Re: After Landing

Sun Apr 16, 2017 2:20 pm

Rajesh123 wrote:
Dears

I was on emirates flight landed at UK. What happened was amazing. After landing, we were out on a field waiting for the bus to arrive. However, I was feeling the pull near the engine fan. Luckily I had a bulky backpack which was probably adding to my weight. And I moved away couple of steps, towards the front of the plane.This is kind of old incident, that happened around 4 years ago.

Can anyone tell me please,
1. is that fan nothing but the engine ?
2. Is the pilot not supposed to switch it off so that people are not pulled towards it
3. Am i thinking too much in that I could have been swallowed in the engine because of the pull.
4. What action should I have taken at that time ?

Sorry, but no chance this happened as you tell it. No engines are running when you as a passenger are on the tarmac around the airplane. Unless that "fan" was a hairdryer belonging to one of the flight attendants.
 
thepinkmachine
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Re: After Landing

Sun Apr 16, 2017 3:41 pm

Jet engine fans are often windmilling in strong wind, when the engines are not running. The rotation may appear quite fast, but it's still a tiny fraction of normal engine speed and in any case the engine doesn't generate any thrust, so there's could be no 'pull' other than normal wind pressure on your body.

Last, but not least, if the engine was really running, there would be helluva noise - no way you could miss it :)
 
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sassiciai
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Re: After Landing

Sun Apr 16, 2017 3:55 pm

I'm sorry, but the thread title "After landing" is quite useless. OP, please amend this and make the title descriptive of the content of the thread, to avoid all of a.net coming here to read this!

Thanks
 
jetmatt777
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Re: After Landing

Sun Apr 16, 2017 4:29 pm

As noted above the engine wasn't on, but it was likely windmilling: rotating as the wind passes through the engine.

I work the ramp and have stood relatively close to running engines (during airstart), there's no appreciable pull on the body from 10-15 feet away. They are just noisy as hell.
Lighten up while you still can, don't even try to understand, just find a place to make your stand and take it easy
 
alggag
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Re: After Landing

Sun Apr 16, 2017 4:36 pm

My hunch is that your big backpack was throwing off your balance slightly and that combined with a bit of wind gave you the impression of being pulled by the engine.
 
Cunard
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Re: Engine Windmilling on the Ramp

Sun Apr 16, 2017 6:55 pm

The OP obviously doesn't travel by air much if he actually believed the engines were on whilst disembarking the aircraft as this situation is a totally common occurence.
 
trav110
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Re: After Landing

Sun Apr 16, 2017 8:25 pm

sassiciai wrote:
I'm sorry, but the thread title "After landing" is quite useless. OP, please amend this and make the title descriptive of the content of the thread, to avoid all of a.net coming here to read this!

Thanks


:sarcastic:

You pedants are never happy.
 
Adispatcher
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Re: Engine Windmilling on the Ramp

Mon Apr 17, 2017 5:26 am

I've stood closer than I probably should have to a running jet engine and never felt any suction or pull as an employee. I doubt it was running, but if it was, I hope you had your earplugs handy.

I was always more concerned about the other end of it, especially when I had the unfortunate experience of standing behind an idling GE90.
 
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lightsaber
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Re: Engine Windmilling on the Ramp

Mon Apr 17, 2017 11:16 am

I'll add that not only was the engine not running and purely windmilling, no airline would endanger passengers as the OP suggests.

Being injested into an engine is a real danger. Engines that must be power windmilled (CFM-56, LEAP, CFM-56) are an extra risk as crew might not notice a start up.

But this was a safe situation.

Lightsaber
"They did not know it was impossible, so they did it!" - Mark Twain
 
Redbellyguppy
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Re: Engine Windmilling on the Ramp

Mon Apr 17, 2017 5:59 pm

It's a testament to how efficient the airfoils are and how exquisitely balanced the N1 is that even a tiny breeze up the tailpipe can turn it backwards. Even when the wind is howling I've never seen it even indicate more than 1.5% on the gauges. The plink plink sounds of certain engines lightly turning backwards is music in the breeze.
 
Wacker1000
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Re: Engine Windmilling on the Ramp

Mon Apr 17, 2017 11:03 pm

Adispatcher wrote:
I've stood closer than I probably should have to a running jet engine and never felt any suction or pull as an employee.


By the time you feel the suction it's too late. ;)
 
MPadhi
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Re: Engine Windmilling on the Ramp

Tue Apr 18, 2017 10:39 am

Out of curiosity, roughly how close would you have to be standing to an engine before it's dangerous at idle or full power? (I wish this would be tested on Mythbusters! :D)
 
BravoOne
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Re: Engine Windmilling on the Ramp

Tue Apr 18, 2017 1:00 pm

Redbellyguppy wrote:
It's a testament to how efficient the airfoils are and how exquisitely balanced the N1 is that even a tiny breeze up the tailpipe can turn it backwards. Even when the wind is howling I've never seen it even indicate more than 1.5% on the gauges. The plink plink sounds of certain engines lightly turning backwards is music in the breeze.


Your right as it might make a person think of wind chimes. The PW JT9's were especially noisy when the wind caused the engines turn over. Sounded more like a fifty gallon drum half filled with nuts and bolts being turned over than anything like a jet engine. The RR were always as quiet as a Swiss watch.
 
kurtverbose
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Re: Engine Windmilling on the Ramp

Tue Apr 18, 2017 3:18 pm

MPadhi wrote:
Out of curiosity, roughly how close would you have to be standing to an engine before it's dangerous at idle or full power? (I wish this would be tested on Mythbusters! :D)


Depends if you're wearing a cape or not.
 
jetmatt777
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Re: Engine Windmilling on the Ramp

Tue Apr 18, 2017 3:43 pm

BravoOne wrote:
Redbellyguppy wrote:
It's a testament to how efficient the airfoils are and how exquisitely balanced the N1 is that even a tiny breeze up the tailpipe can turn it backwards. Even when the wind is howling I've never seen it even indicate more than 1.5% on the gauges. The plink plink sounds of certain engines lightly turning backwards is music in the breeze.


Your right as it might make a person think of wind chimes. The PW JT9's were especially noisy when the wind caused the engines turn over. Sounded more like a fifty gallon drum half filled with nuts and bolts being turned over than anything like a jet engine. The RR were always as quiet as a Swiss watch.


I love the clinking sound of the CF-34's on the CRJ-700.
Lighten up while you still can, don't even try to understand, just find a place to make your stand and take it easy
 
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TWA772LR
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Re: Engine Windmilling on the Ramp

Tue Apr 18, 2017 3:46 pm

MPadhi wrote:
Out of curiosity, roughly how close would you have to be standing to an engine before it's dangerous at idle or full power? (I wish this would be tested on Mythbusters! :D)

Would be a cool way for Kalitta to do a final send-off for its last 742!
kurtverbose wrote:
MPadhi wrote:
Out of curiosity, roughly how close would you have to be standing to an engine before it's dangerous at idle or full power? (I wish this would be tested on Mythbusters! :D)


Depends if you're wearing a cape or not.

The Incredibles is definitely Pixar's most underrated movie. ;)
Eat 'em up Kats!
 
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Horstroad
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Re: Engine Windmilling on the Ramp

Wed Apr 19, 2017 9:33 pm

MPadhi wrote:
Out of curiosity, roughly how close would you have to be standing to an engine before it's dangerous at idle or full power? (I wish this would be tested on Mythbusters! :D)

I think it must be pretty close. I've seen candy wrap swirling on the ground below the inlet in the ground vortex of a CF6 at idle. The suction was not strong enough to pull it in. I wouldn't trust my life on this observation and test it out though. I trust the red line on the engine and the placard telling me to stay 15ft away.
They always say that the smaller engines are more dangerous. I don't know if it is because their strength is underestimated or because a body blocks a bigger percentage of the inlet area thus creating a stronger suction force.
 
gtae07
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Re: Engine Windmilling on the Ramp

Thu Apr 20, 2017 12:15 am

BravoOne wrote:
The RR were always as quiet as a Swiss watch.

You've never heard a Tay in the breeze, have you?

CLANKCLANKCLANKCLANKCLANKCLANKCLANKCLANKCLANKCLANKCLANKCLANKCLANKCLANKCLANKCLANK.....
 
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Balerit
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Re: Engine Windmilling on the Ramp

Thu Apr 20, 2017 11:26 am

A friend of mine was sucked into a JT3 while doing the headset on a ground run, the copco he was sitting in was too close to the engine and when he exited the vehicle he got sucked in. Not nice, he lost both arms.
Licensed Aircraft Maintenance Engineer (retired).
 
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767333ER
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Re: Engine Windmilling on the Ramp

Thu Apr 20, 2017 2:15 pm

BravoOne wrote:
Redbellyguppy wrote:
It's a testament to how efficient the airfoils are and how exquisitely balanced the N1 is that even a tiny breeze up the tailpipe can turn it backwards. Even when the wind is howling I've never seen it even indicate more than 1.5% on the gauges. The plink plink sounds of certain engines lightly turning backwards is music in the breeze.


Your right as it might make a person think of wind chimes. The PW JT9's were especially noisy when the wind caused the engines turn over. Sounded more like a fifty gallon drum half filled with nuts and bolts being turned over than anything like a jet engine. The RR were always as quiet as a Swiss watch.

You must have never heard the RRs that had narrow chord fans with clappers. I love the sound of clappers...
Been on: 732 733 734 73G 738 752 763 A319 A320 A321 CRJ CR7 CRA/CR9 E145 E175 E190 F28 MD-82 MD-83 C172R C172S P2006T
 
thepinkmachine
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Re: Engine Windmilling on the Ramp

Thu Apr 20, 2017 6:13 pm

Balerit wrote:
A friend of mine was sucked into a JT3 while doing the headset on a ground run, the copco he was sitting in was too close to the engine and when he exited the vehicle he got sucked in. Not nice, he lost both arms.



I seem to remember reading that old-style narrow engines were more dangerous than the contemporary ones with larger fan, as for given mass flow you needed higher intake velocity, hence stronger suction...
 
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thefactorypilot
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Re: Engine Windmilling on the Ramp

Fri Apr 21, 2017 12:58 pm

Redbellyguppy wrote:
It's a testament to how efficient the airfoils are and how exquisitely balanced the N1 is that even a tiny breeze up the tailpipe can turn it backwards. Even when the wind is howling I've never seen it even indicate more than 1.5% on the gauges. The plink plink sounds of certain engines lightly turning backwards is music in the breeze.

THeres NO way that was even an accurate indication. It would have to be a wind of a hundred miles per hour to register rotation on the fan gauges.

On the CF34-8C5 the book even says that N1 indications below something like 5% are to be considered unreliable.
 
Redbellyguppy
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Re: Engine Windmilling on the Ramp

Sat Apr 22, 2017 4:33 am

We had 14 knots more or less straight up the pipe today and were showing 1.5-1.6 N1. I don't know if it's accurate or not, but neither Bulfer's book nor our FlIght Reference Manual say that it is unreliable when windmilling in reverse. I'm just reading what it off the display.
 
Redbellyguppy
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Re: Engine Windmilling on the Ramp

Sat Apr 22, 2017 8:36 am

1.5% n1 would only be about 80 rpm. That's totally doable in a good breeze.
 
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thefactorypilot
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Re: Engine Windmilling on the Ramp

Sat Apr 22, 2017 3:32 pm

Redbellyguppy wrote:
1.5% n1 would only be about 80 rpm. That's totally doable in a good breeze.

Fans spin at tens of thousands of RPM... I'd have to look to see what the percentage equals in RMP on the cf34, but I can tell you that 1.5 percent of actual rotation would still be hundreds of RPMs.
 
SAAFNAV
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Re: Engine Windmilling on the Ramp

Sat Apr 22, 2017 4:16 pm

thefactorypilot wrote:
Redbellyguppy wrote:
1.5% n1 would only be about 80 rpm. That's totally doable in a good breeze.

Fans spin at tens of thousands of RPM... I'd have to look to see what the percentage equals in RMP on the cf34, but I can tell you that 1.5 percent of actual rotation would still be hundreds of RPMs.



No, the N2 core spins at that high speeds. The fan is relatively low speed.

Discussions point to the GE90-115 having a 100% N1 of 2 355 rpm, and a CFM56-5B4 seems to 5 200 rpm.
I'll leave you to calculate 1% of that.

In lieu of flight manuals, refer to this:

http://www.pprune.org/tech-log/329783-r ... 115bl.html
www.pprune.org/questions/204270-q-turbo ... 6-5b4.html
L-382 Loadmaster; ex C-130B Navigator
 
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HAWK21M
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Re: Engine Windmilling on the Ramp

Sat Apr 22, 2017 7:16 pm

Every Aircraft Engine has the Danger zones or safety path marked in the respective manuals under various thrust conditions.
In the case described in OP , its clearly just windmilling & unlikely the engine was running, the Pax would all be well away from the restricted zone.
However from a technical POV, windmilling over a long duration can reduces the lubrication in the bearings & ideal to install engine covers for longer halts.
I may not win often, but I damn well never lose!!! ;)
 
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FriscoHeavy
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Re: Engine Windmilling on the Ramp

Sat Apr 22, 2017 10:48 pm

What happened to Rajesh123? He disappeared. Did he get sucked into a windmilling engine after he posted?
FriscoHeavy
 
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akiss20
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Re: Engine Windmilling on the Ramp

Sun Apr 23, 2017 12:16 am

thefactorypilot wrote:
Redbellyguppy wrote:
1.5% n1 would only be about 80 rpm. That's totally doable in a good breeze.

Fans spin at tens of thousands of RPM... I'd have to look to see what the percentage equals in RMP on the cf34, but I can tell you that 1.5 percent of actual rotation would still be hundreds of RPMs.


The only fans that spin in the 10,000-20,000 RPM range are small fan diameter engines for very small business jets, on the 1500-2500 lbf thrust class (think Eclipse 500, Citation Mustang etc).
Change will not come if we wait for some other person or some other time. We are the ones we've been waiting for. We are
 
StereoTechque
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Re: Engine Windmilling on the Ramp

Sun Apr 23, 2017 7:54 am

FriscoHeavy wrote:
What happened to Rajesh123? He disappeared. Did he get sucked into a windmilling engine after he posted?


:lol: As far as windmilling on ramp goes the PW GTF is protected from it due the bearing loaded N1 shaft.
Looking California.. Feeling Minnesota.... R. I.P. Chris Cornell...
 
benbeny
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Re: Engine Windmilling on the Ramp

Sun Apr 23, 2017 11:39 am

Is there any side effects for engines windmilling? How bad is that, and why don't they put brakes to stop it from rotating?
 
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Starlionblue
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Re: Engine Windmilling on the Ramp

Sun Apr 23, 2017 11:59 am

benbeny wrote:
Is there any side effects for engines windmilling? How bad is that, and why don't they put brakes to stop it from rotating?


The potential problem is a lack of lubrication. If you're talking a turnaround and the engine still warm, windmilling slowly won't matter much. A bit like turning a car engine around very slowly doesn't do very much to it, especially when still warm and lubricated. Sure, you need oil when it is going 1000s of RPM, but just slowly ticking around is nothing.

There are no brakes. If the engine will be sitting still for a longer period, covers are fitted. Or you take the engine (typically with the plane still attached) indoors out of the wind.
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