Topic Author
Posts: 347
Joined: Sat Oct 26, 2013 2:44 pm

### What is a maximum engine fan diameter on A350 & 787?

That is for future reengining. A350 looks somewhat taller than 787 but a little bit lower than 777. My free and outsider projection is about 310cm(122") for 787 and 340cm(134") for A350 but I want to know about potential and the limits of both.

Posts: 475
Joined: Thu Apr 20, 2017 5:14 pm

### Re: What is a maximum engine fan diameter on A350 & 787?

787 all three version have different landing gear and different fuselage clearance. actually 781 engines have bigger clearance than 789.

in general, unlike 737, its not about current fuselage/wing clearance but how they able to lift plane for more clearance without losing grandfathering (evacuation rafts and other equipment).
i believe for both 787 and 350 they secure some extra room for this, we dont know how much and its pointless to divine without more info.

DocLightning
Posts: 21513
Joined: Wed Nov 16, 2005 8:51 am

### Re: What is a maximum engine fan diameter on A350 & 787?

From this document: https://www.boeing.com/resources/boeing ... ps/787.pdf

On the 788 there are 0.74 and 0.71 meters clearance between the bottom of the engine cowling and the ground for GE and RR, respectively at max taxi weight.
For the 789 there are 0.69 and 0.71 meters clearance for GE and RR, respectively. (at minimum weight it's 0.76 and 0.79, so I'm puzzled).
For the 78J there are 0.74 meters clearance for each.
-Doc Lightning-

"The sky calls to us. If we do not destroy ourselves, we will one day venture to the stars."
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zeke
Posts: 13903
Joined: Thu Dec 14, 2006 1:42 pm

### Re: What is a maximum engine fan diameter on A350 & 787?

That is for future reengining. A350 looks somewhat taller than 787 but a little bit lower than 777. My free and outsider projection is about 310cm(122") for 787 and 340cm(134") for A350 but I want to know about potential and the limits of both.

I had a look at the spanwise centreline from the outer wheel to the spanwise centre of the engine, and the minimum height of the engine off the ground I came up with the following maximum angles which would be the landing roll angle limits.

Spanwise distance from the outer main wheel to the engine centre line (mm)

787-8 4180
787-9 4250
787-10 4050
A350-900 4330
A350-1000 4400

Minimum height of engine from ground (mm)

787-8 710
787-9 610
787-10 740
A350-900 760
A350-1000 760

Minimum angle from wheels to engine (maximum bank angle limited in landing), in degrees

787-8 9.64
787-9 8.17
787-10 10.35
A350-900 9.96
A350-1000 9.80

The most limited aircraft appears to be the 787-9.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

RJMAZ
Posts: 1565
Joined: Sat Jul 09, 2016 2:54 am

### Re: What is a maximum engine fan diameter on A350 & 787?

zeke wrote:
The most limited aircraft appears to be the 787-9.

The 787-9 and 787-10 have the same gear? The numbers should be the same.

Posts: 475
Joined: Thu Apr 20, 2017 5:14 pm

### Re: What is a maximum engine fan diameter on A350 & 787?

RJMAZ wrote:
zeke wrote:
The most limited aircraft appears to be the 787-9.

The 787-9 and 787-10 have the same gear? The numbers should be the same.

no. each variant (-8, -9, -10) have different fuselage clearance and another difference on load

RJMAZ
Posts: 1565
Joined: Sat Jul 09, 2016 2:54 am

### Re: What is a maximum engine fan diameter on A350 & 787?

RJMAZ wrote:
zeke wrote:
The most limited aircraft appears to be the 787-9.

The 787-9 and 787-10 have the same gear? The numbers should be the same.

no. each variant (-8, -9, -10) have different fuselage clearance and another difference on load

No the landing gear for the 9/10 is the same. They even use the same tyres.

The difference in ground clearance is because the nose gear is further away from the MLG on the -10.

Posts: 475
Joined: Thu Apr 20, 2017 5:14 pm

### Re: What is a maximum engine fan diameter on A350 & 787?

RJMAZ wrote:
RJMAZ wrote:
The 787-9 and 787-10 have the same gear? The numbers should be the same.

no. each variant (-8, -9, -10) have different fuselage clearance and another difference on load

No the landing gear for the 9/10 is the same. They even use the same tyres.

The difference in ground clearance is because the nose gear is further away from the MLG on the -10.

https://www.boeing.com/resources/boeing ... ps/787.pdf
thank you
ok, nose gear lower than main. and for -10 its 3 more meter ahead.
but if the main gear height will be same point H must be lower on -10.

i tried to calculate some numbers basing on this ACAP but find out i cant understand it at all.
how point E can be much more movement on load than D and F

so i just stop trying.

still hard to believe gear is the same (tyres of cource yes) but cand find out more.

flipdewaf
Posts: 2846
Joined: Thu Jul 20, 2006 6:28 am

### Re: What is a maximum engine fan diameter on A350 & 787?

Wouldn't it make more sense to look at the distance to the underside of the wing as any re-engine effort (assuming that's why we are looking at this) would surely redesign the structural pylon and aerodynamic interface as was done for the A330NEO and the extreme example of the 737?

Fred

zeke
Posts: 13903
Joined: Thu Dec 14, 2006 1:42 pm

### Re: What is a maximum engine fan diameter on A350 & 787?

RJMAZ wrote:
zeke wrote:
The most limited aircraft appears to be the 787-9.

The 787-9 and 787-10 have the same gear? The numbers should be the same.

Incorrect, look at charts 2.2.1-2.2.3, the span wise location of the engine are (mm)

787-8 - 9730
787-9 - 9910
787-10 - 9710

As the 787-9:engine is further out it will hit the ground before other models in roll.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

RJMAZ
Posts: 1565
Joined: Sat Jul 09, 2016 2:54 am

### Re: What is a maximum engine fan diameter on A350 & 787?

You learn something new every day.

Who would have thought the 787-9 has a different wing, pylon with the engine moved further out.

Everything I heard the 787-10 was a simple stretch of the 787-9 and the commonality is extremely high. It would be great if someone can explain why or if it is an error in the ACAP.

LH707330
Posts: 2200
Joined: Fri Jun 15, 2012 11:27 pm

### Re: What is a maximum engine fan diameter on A350 & 787?

RJMAZ wrote:
You learn something new every day.

Who would have thought the 787-9 has a different wing, pylon with the engine moved further out.

Everything I heard the 787-10 was a simple stretch of the 787-9 and the commonality is extremely high. It would be great if someone can explain why or if it is an error in the ACAP.

I'd stack my chips on ACAP error, why ould the -9 have engines further out and the other two have roughly the same engine spacing?

RJMAZ
Posts: 1565
Joined: Sat Jul 09, 2016 2:54 am

### Re: What is a maximum engine fan diameter on A350 & 787?

LH707330 wrote:
RJMAZ wrote:
You learn something new every day.

Who would have thought the 787-9 has a different wing, pylon with the engine moved further out.

Everything I heard the 787-10 was a simple stretch of the 787-9 and the commonality is extremely high. It would be great if someone can explain why or if it is an error in the ACAP.

I'd stack my chips on ACAP error, why ould the -9 have engines further out and the other two have roughly the same engine spacing?

Agreed. I'll assume the 787-9 and 10 are the same.

So in terms of bank angle the 787-10 is better than the A350 for ground clearance.

787-10 10.35 degrees
A350-900 9.96 degrees
A350-1000 9.80 degrees

This completely shuts down the argument that the 787 can not get next gen engines. Both will easily be able to accept larger fan diameter and 14:1 bypass ratio engines.

zeke
Posts: 13903
Joined: Thu Dec 14, 2006 1:42 pm

### Re: What is a maximum engine fan diameter on A350 & 787?

LH707330 wrote:
I'd stack my chips on ACAP error, why ould the -9 have engines further out and the other two have roughly the same engine spacing?

Due to different fuselage lengths the bow wave location is different. The optimum spanwise position for the engine changes depending on the bow wave.

RJMAZ wrote:
This completely shuts down the argument that the 787 can not get next gen engines. Both will easily be able to accept larger fan diameter and 14:1 bypass ratio engines.

You cannot jump to such a conclusion, you need to look at a numbers of different geometric considerations, the 787-10 is much more limited in pitch.
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

tommy1808
Posts: 10777
Joined: Thu Nov 21, 2013 3:24 pm

### Re: What is a maximum engine fan diameter on A350 & 787?

RJMAZ wrote:
This completely shuts down the argument that the 787 can not get next gen engines. .

only as far as role is concerned..... it still has engines a bit closer to the ground, and, hard to judge from the ACAP drawings, already sitting higher relative to the wing. Of course there could be aerodynamic reasons why it can´t be higher on the A350 and could be still higher on the 787.... but we will see.

best regards
Thomas
This Singature is a safe space......

RJMAZ
Posts: 1565
Joined: Sat Jul 09, 2016 2:54 am

### Re: What is a maximum engine fan diameter on A350 & 787?

tommy1808 wrote:
only as far as role is concerned..... it still has engines a bit closer to the ground

Roll would be the only criteria determining the minimum engine distance to the ground.

There is no other way for the engine to hit the ground besides excessive roll from a side wind landing. A nose landing gear collapse would see the current engines hit the ground.

As the engines are forward of the main landing any pitch increases the distance to the ground. Tail strike might be the biggest issue with a 787-11.

The 787 engines being smaller diameter and lower thrust than the A350 might even allow a higher bypass ratio than the while maintaining say a 9 degree max roll angle.

Erebus
Posts: 1032
Joined: Tue Oct 20, 2015 2:40 am

### Re: What is a maximum engine fan diameter on A350 & 787?

RJMAZ wrote:
LH707330 wrote:
RJMAZ wrote:
You learn something new every day.

Who would have thought the 787-9 has a different wing, pylon with the engine moved further out.

Everything I heard the 787-10 was a simple stretch of the 787-9 and the commonality is extremely high. It would be great if someone can explain why or if it is an error in the ACAP.

I'd stack my chips on ACAP error, why ould the -9 have engines further out and the other two have roughly the same engine spacing?

Agreed. I'll assume the 787-9 and 10 are the same.

So in terms of bank angle the 787-10 is better than the A350 for ground clearance.

787-10 10.35 degrees
A350-900 9.96 degrees
A350-1000 9.80 degrees

This completely shuts down the argument that the 787 can not get next gen engines. Both will easily be able to accept larger fan diameter and 14:1 bypass ratio engines.

787-10 may accept. But the same cannot go on the 787-9. You're still going to need to modify the latter if the same larger sized engine is to apply to both.

tommy1808
Posts: 10777
Joined: Thu Nov 21, 2013 3:24 pm

### Re: What is a maximum engine fan diameter on A350 & 787?

RJMAZ wrote:
tommy1808 wrote:
only as far as role is concerned..... it still has engines a bit closer to the ground

Roll would be the only criteria determining the minimum engine distance to the ground.

You kinda want to make sure that you have no risk of running you engines into obstacles on the ground either...
And of course being able to move the engines up a bit relative to the wing preserves room to roll.

Best regards
Thomas
This Singature is a safe space......

LH707330
Posts: 2200
Joined: Fri Jun 15, 2012 11:27 pm

### Re: What is a maximum engine fan diameter on A350 & 787?

zeke wrote:
LH707330 wrote:
I'd stack my chips on ACAP error, why ould the -9 have engines further out and the other two have roughly the same engine spacing?

Due to different fuselage lengths the bow wave location is different. The optimum spanwise position for the engine changes depending on the bow wave.

RJMAZ wrote:
This completely shuts down the argument that the 787 can not get next gen engines. Both will easily be able to accept larger fan diameter and 14:1 bypass ratio engines.

You cannot jump to such a conclusion, you need to look at a numbers of different geometric considerations, the 787-10 is much more limited in pitch.

Hmm, interesting point. How would it make sense though for the 8 and 10 to be about the same, but the 9 to be spaced so much further out? Are you aware of other types having engines mounted differently in the stretched versions?

zeke
Posts: 13903
Joined: Thu Dec 14, 2006 1:42 pm

### Re: What is a maximum engine fan diameter on A350 & 787?

LH707330 wrote:
Are you aware of other types having engines mounted differently in the stretched versions?

Spanwise location of inner engine

77W - 9610 mm
779 - 10640 mm

744 - 11640 mm
748 - 11840 mm
Human rights lawyers are "ambulance chasers of the very worst kind.'" - Sky News

RJMAZ
Posts: 1565
Joined: Sat Jul 09, 2016 2:54 am

### Re: What is a maximum engine fan diameter on A350 & 787?

tommy1808 wrote:
You kinda want to make sure that you have no risk of running you engines into obstacles on the ground either...
And of course being able to move the engines up a bit relative to the wing preserves room to roll.

Best regards
Thomas

Ground obstacles wouldn't be an issue either. The 787 already has twice the ground clearance of an A320NEO. So it would 99% be due roll on landing.

The 787 is good to go for next gen engines. The 787 probably has a few more inchs room in the downward direction than the A350 due to the MLG allowing the engine to go closer to the ground. The A350 however has a few more inchs in the upwards direction due to a slightly longer pylon.

Both aircraft will easily fit fans that are 10% bigger in diameter allowing 14:1 bypass ratios to keep the same thrust level.

787 can go up 10% from 112inch to 123inch.
A350 can go up 10% from 118inch to 130inch.

LH707330
Posts: 2200
Joined: Fri Jun 15, 2012 11:27 pm

### Re: What is a maximum engine fan diameter on A350 & 787?

zeke wrote:
LH707330 wrote:
Are you aware of other types having engines mounted differently in the stretched versions?

Spanwise location of inner engine

77W - 9610 mm
779 - 10640 mm

744 - 11640 mm
748 - 11840 mm

Thanks for those numbers. On the 777, the wing is entirely new, I'm curious if there are examples where the wing is the same and the fuselage length is the only variable. I'll go do some digging this weekend.

WIederling
Posts: 8693
Joined: Sun Sep 13, 2015 2:15 pm

### Re: What is a maximum engine fan diameter on A350 & 787?

zeke wrote:
Spanwise location of inner engine
77W - 9610 mm
779 - 10640 mm

744 - 11640 mm
748 - 11840 mm

both examples have either strongly redesigned or new wings.
Afair the 779 also has a wider MLG foot print?

apropos: did engine centers change from CEO to NEO ? ( for A320, A330 )
Murphy is an optimist

CowAnon
Posts: 73
Joined: Fri Nov 03, 2017 12:03 am

### Re: What is a maximum engine fan diameter on A350 & 787?

From Clean Sky, The UHBR engine flight testing programme gathers momentum, January 21, 2019:
https://www.cleansky.eu/the-uhbr-engine-flight-testing-programme-gathers-momentum

3.55 meters = 139.8 inches. I'm assuming that figure refers to just the fan diameter, not the overall nacelle diameter. Since Airbus is involved in this Clean Sky project, you'd think they would make sure the UltraFan would be compatible with the A350 in its current state.

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