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Small Rudder Size On DC10 / MD11  
User currently offlineYQBexYHZBGM From Canada, joined May 2009, 204 posts, RR: 1
Posted (1 year 3 months 2 days 13 hours ago) and read 6828 times:

This is a question I've been wondering about for some time:

Obviously, the tail-mounted engine limits the size of the rudder on the DC10 / MD11, but how did they get away with using such a small rudder on such a large aircraft? I'm surprised they didn't require a much larger vertical stabilizer to accommodate both the engine and a larger rudder. The small size of the rudder and the vertical stabilizer as a whole is very evident as compared with the L1011.

Also, is there a special technical name for the rectangular piece that extends rearward from the tail above the engine but below the rudder? What is its aerodynamic function?

Al
YQBexYHZBGM

39 replies: All unread, showing first 25:
 
User currently offlineYQBexYHZBGM From Canada, joined May 2009, 204 posts, RR: 1
Reply 1, posted (1 year 3 months 2 days 12 hours ago) and read 6750 times:

My apologies, I just discovered there was a similar thread in 2002. But, if anyone wishes to continue the conversation, please go ahead.

Al


User currently offlinePITrules From United States of America, joined Jun 2000, 3254 posts, RR: 6
Reply 2, posted (1 year 3 months 2 days 12 hours ago) and read 6742 times:

Quoting YQBexYHZBGM (Thread starter):
The small size of the rudder and the vertical stabilizer as a whole is very evident as compared with the L1011.

The engines on the L-1011 are further out on the wing than that of the DC-10. This would create more yaw during an engine failure on the L-1011 necessitating a larger rudder.



FLYi
User currently offlinezanl188 From United States of America, joined Oct 2006, 3588 posts, RR: 0
Reply 3, posted (1 year 3 months 2 days 11 hours ago) and read 6733 times:
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DC-10 & MD-11 rudders are double hinged. Makes them more effective than a conventional rudder of the same size.


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Photo © Alastair T. Gardiner - WorldAirImages




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User currently offlinemd11sdf From United States of America, joined Dec 2006, 83 posts, RR: 0
Reply 4, posted (1 year 3 months 2 days 10 hours ago) and read 6650 times:

The structure that extends aft, below the rudder contains the aft mount/support for the number two engine.
It serves zero "aerodynamic-function"

Cheers from Louisville (KSDF) home to the UPS Worldport AND the MD-11 fleet.



LOUISVILLE, where your camera may as well be a stinger misslie to the Airport Police.
User currently offlineYQBexYHZBGM From Canada, joined May 2009, 204 posts, RR: 1
Reply 5, posted (1 year 3 months 2 days 9 hours ago) and read 6613 times:

Thanks all! That's about the fastest any of my questions have ever gotten answered -- 3 posts, done!  

-Al


User currently offlinejetmech From Australia, joined Mar 2006, 2699 posts, RR: 53
Reply 6, posted (1 year 3 months 2 days 7 hours ago) and read 6564 times:

Quoting PITrules (Reply 2):
The engines on the L-1011 are further out on the wing than that of the DC-10. This would create more yaw during an engine failure on the L-1011 necessitating a larger rudder.

I was of the impression that it was the larger rudder itself that permitted the L1011's engines to be further out on the wing?

IIRC, the lower mounting of the L1011 centreline engine allowed for a rudder of much greater height. This in turn allowed the engines to be further out on the wing, the benefit of this being extra bending moment relief that ultimately provided the opportunity for a lighter wing structure.

Regards, JetMech



JetMech split the back of his pants. He can feel the wind in his hair.
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17172 posts, RR: 66
Reply 7, posted (1 year 3 months 2 days 7 hours ago) and read 6557 times:

Quoting jetmech (Reply 6):
IIRC, the lower mounting of the L1011 centreline engine allowed for a rudder of much greater height. This in turn allowed the engines to be further out on the wing, the benefit of this being extra bending moment relief that ultimately provided the opportunity for a lighter wing structure.

Indeed. The lower rudder mounting also meant less rudder-induced roll moment.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineMax Q From United States of America, joined May 2001, 4778 posts, RR: 19
Reply 8, posted (1 year 3 months 2 days 6 hours ago) and read 6528 times:

Quoting YQBexYHZBGM (Thread starter):
This is a question I've been wondering about for some time:

Obviously, the tail-mounted engine limits the size of the rudder on the DC10 / MD11, but how did they get away with using such a small rudder on such a large aircraft? I'm surprised they didn't require a much larger vertical stabilizer to accommodate both the engine and a larger rudder. The small size of the rudder and the vertical stabilizer as a whole is very evident as compared with the L1011.

As Zan said, MD had to use a double hinged rudder to compensate for it's smaller size.


It's also why the wing engines are as close as possible to the fuselage (unlike the L1011) so the engine failure induced yaw case would be the lowest possible that this relatively 'weak' rudder would have to cope with.



The best contribution to safety is a competent Pilot.
User currently offlinePGNCS From United States of America, joined Apr 2007, 2858 posts, RR: 49
Reply 9, posted (1 year 3 months 1 day 20 hours ago) and read 6406 times:

Quoting jetmech (Reply 6):
Quoting PITrules (Reply 2):The engines on the L-1011 are further out on the wing than that of the DC-10. This would create more yaw during an engine failure on the L-1011 necessitating a larger rudder.
I was of the impression that it was the larger rudder itself that permitted the L1011's engines to be further out on the wing?

IIRC, the lower mounting of the L1011 centreline engine allowed for a rudder of much greater height. This in turn allowed the engines to be further out on the wing, the benefit of this being extra bending moment relief that ultimately provided the opportunity for a lighter wing structure.
Quoting Starlionblue (Reply 7):
Quoting jetmech (Reply 6):IIRC, the lower mounting of the L1011 centreline engine allowed for a rudder of much greater height. This in turn allowed the engines to be further out on the wing, the benefit of this being extra bending moment relief that ultimately provided the opportunity for a lighter wing structure.

Indeed. The lower rudder mounting also meant less rudder-induced roll moment.

Indeed, gentlemen. All of which had the nice side effect of less FOD potential for the L-1011 (as they are higher off the ground as they moved out and up the wing) and a quieter cabin as they are farther from the fuselage. I can personally testify that the rudder on the L-1011 is EXTREMELY effective.


User currently offlineroseflyer From United States of America, joined Feb 2004, 9803 posts, RR: 52
Reply 10, posted (1 year 3 months 1 day 19 hours ago) and read 6380 times:

Another factor is that rudders are sized for an engine out condition on takeoff. With the trijet configuration, the effect of an engine out is less dramatic than on a twin, or a quad with the outboard engine inoperative. The smallest rudders are always on airplanes with tail mounted engines. The 777 with its gigantic engines has to have a very large rudder because so much yaw is induced at takeoff thrust with an engine out. Similarly, despite being less powerful, the moment generated from losing an outboard engine on a 747 is quite large, and requires quite a bit of rudder.


If you have never designed an airplane part before, let the real designers do the work!
User currently offlinePGNCS From United States of America, joined Apr 2007, 2858 posts, RR: 49
Reply 11, posted (1 year 3 months 1 day 16 hours ago) and read 6300 times:

Quoting roseflyer (Reply 10):
Another factor is that rudders are sized for an engine out condition on takeoff.
Quoting roseflyer (Reply 10):
The smallest rudders are always on airplanes with tail mounted engines.

Very concisely stated. The fact that the L-1011 was able to easily have such a giant rudder due to the lower placement of engine 2 allows far more asymmetric thrust moment than could be tolerated by a DC-10 even with it's articulated rudder, hence the relative engine positions on engines 1 and 3 on the two types.


User currently offlineWestern727 From United States of America, joined Jan 2007, 753 posts, RR: 4
Reply 12, posted (1 year 3 months 1 day 15 hours ago) and read 6266 times:

Quoting roseflyer (Reply 10):
Similarly, despite being less powerful, the moment generated from losing an outboard engine on a 747 is quite large, and requires quite a bit of rudder.

...and this is why the 747SP's vert stab is even larger than the non-SP - since the SP fuselage is shorter, the "tail" has to be bigger (in this case they just made it a few feet taller) to compensate. Further, I suspect this is why the SP's rudder is double-hinged since it appears NOT to be taller than that of the non-SP 747 - only the vert stab itself is taller.



Jack @ AUS
User currently offlineLH707330 From United States of America, joined Jun 2012, 848 posts, RR: 0
Reply 13, posted (1 year 3 months 1 day 15 hours ago) and read 6255 times:

Quoting Western727 (Reply 12):
...and this is why the 747SP's vert stab is even larger than the non-SP - since the SP fuselage is shorter, the "tail" has to be bigger (in this case they just made it a few feet taller) to compensate. Further, I suspect this is why the SP's rudder is double-hinged since it appears NOT to be taller than that of the non-SP 747 - only the vert stab itself is taller.

Same story with the A318, the taller fin provides lift, and thus directional stability, when there is an off-center angle of attack over the fin, e.g. engine out. The lower rudder on the 748i is likewise double-hinged, so they could retain most of the structure from the 744.


User currently offlineViscount724 From Switzerland, joined Oct 2006, 25983 posts, RR: 22
Reply 14, posted (1 year 3 months 1 day 9 hours ago) and read 6126 times:

Quoting Western727 (Reply 12):
Quoting roseflyer (Reply 10):
Similarly, despite being less powerful, the moment generated from losing an outboard engine on a 747 is quite large, and requires quite a bit of rudder.

...and this is why the 747SP's vert stab is even larger than the non-SP - since the SP fuselage is shorter, the "tail" has to be bigger (in this case they just made it a few feet taller) to compensate. Further, I suspect this is why the SP's rudder is double-hinged since it appears NOT to be taller than that of the non-SP 747 - only the vert stab itself is taller.

In addition to the 5 ft. taller vertical stabilizer, the SP's horizontal stabilizer is also much larger than on other 747 models. Span is 10 ft. greater (82.9 ft. instead of 72.9 ft.) I think the elevators are the same size but the stabilizer structure extends another 5 ft. on each side beyond the end of the elevator. Illustrated on the photo below. Can also see the SP's much simpler single-slotted flaps which lack the big canoe fairings for the mechanism that other 747 models have.



[Edited 2013-09-17 19:25:18]

[Edited 2013-09-17 19:27:36]

User currently offlinebohica From United States of America, joined Feb 2004, 2748 posts, RR: 0
Reply 15, posted (1 year 3 months 1 day 8 hours ago) and read 6114 times:

I have noticed a "dip" on the -SP fuselage at the tail which is not on the other 747 variants. You can see it in this picture:


View Large View Medium
Click here for bigger photo!

Photo © Raymond Ngu



Is that dip also to give the -SP extra vertical stabilizer area without adding too much height?


User currently offlineStarlionblue From Greenland, joined Feb 2004, 17172 posts, RR: 66
Reply 16, posted (1 year 3 months 1 day 8 hours ago) and read 6104 times:

Quoting bohica (Reply 15):
Is that dip also to give the -SP extra vertical stabilizer area without adding too much height?

Yepp.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinebohica From United States of America, joined Feb 2004, 2748 posts, RR: 0
Reply 17, posted (1 year 3 months 1 day 8 hours ago) and read 6099 times:

Quoting Starlionblue (Reply 16):
Yepp.

Thanks.  


User currently offlineLH707330 From United States of America, joined Jun 2012, 848 posts, RR: 0
Reply 18, posted (1 year 3 months 19 hours ago) and read 5953 times:

Quoting Starlionblue (Reply 16):
Quoting bohica (Reply 15):
Is that dip also to give the -SP extra vertical stabilizer area without adding too much height?

Yepp.

Does it also help with area ruling?


User currently offlinezanl188 From United States of America, joined Oct 2006, 3588 posts, RR: 0
Reply 19, posted (1 year 3 months 12 hours ago) and read 5823 times:
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Quoting Starlionblue (Reply 16):
Yepp.

What? Are you sure?

My understanding of the "dip" was that it was a design compromise to use existing structure. Since the rear fuselage of the SP was so much shorter there wasn't enough length to use the existing keel "slope" AND have the crown of the fuselage line up. So the entire rear fuselage sits lower compared to the rest of the fuselage. Note how much lower the H-stab sits on the SP as compared to the full length 747 (line it up with door and window belt).



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User currently offlineStarlionblue From Greenland, joined Feb 2004, 17172 posts, RR: 66
Reply 20, posted (1 year 3 months 11 hours ago) and read 5803 times:

Quoting zanl188 (Reply 19):
Quoting Starlionblue (Reply 16):
Yepp.

What? Are you sure?

My understanding of the "dip" was that it was a design compromise to use existing structure. Since the rear fuselage of the SP was so much shorter there wasn't enough length to use the existing keel "slope" AND have the crown of the fuselage line up. So the entire rear fuselage sits lower compared to the rest of the fuselage. Note how much lower the H-stab sits on the SP as compared to the full length 747 (line it up with door and window belt).

You may be right, but I have never heard this.

Quoting LH707330 (Reply 18):
Quoting Starlionblue (Reply 16):

Quoting bohica (Reply 15):
Is that dip also to give the -SP extra vertical stabilizer area without adding too much height?

Yepp.

Does it also help with area ruling?

No idea. Frankly at the tail area ruling goes out of the window a bit given the empennage.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinezanl188 From United States of America, joined Oct 2006, 3588 posts, RR: 0
Reply 21, posted (1 year 3 months 10 hours ago) and read 5784 times:
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Quoting Starlionblue (Reply 20):
You may be right, but I have never heard this.

Please explain. To do as you suggest would have required a redesign of the ENTIRE rear fuselage when a simple plug at the base of the v-stab would have provided any additional area required.



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User currently offlineStarlionblue From Greenland, joined Feb 2004, 17172 posts, RR: 66
Reply 22, posted (1 year 3 months 10 hours ago) and read 5764 times:

Quoting zanl188 (Reply 21):
Quoting Starlionblue (Reply 20):
You may be right, but I have never heard this.

Please explain. To do as you suggest would have required a redesign of the ENTIRE rear fuselage when a simple plug at the base of the v-stab would have provided any additional area required.

Shifting the burden of proof?  

As I said, you may be right. I may be wrong. I'm not sure of anything anymore! 



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinezanl188 From United States of America, joined Oct 2006, 3588 posts, RR: 0
Reply 23, posted (1 year 3 months 9 hours ago) and read 5754 times:
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Quoting Starlionblue (Reply 22):

This is Tech Ops, please explain why the dip to enhance v-stab area.

Section 48 of the SP is structurally unchanged from a standard 747. Because of this the proceeding barrel section had to be recontoured, thus the dip. Please check the usual 747 books and sources for confirmation.



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User currently offlineStarlionblue From Greenland, joined Feb 2004, 17172 posts, RR: 66
Reply 24, posted (1 year 3 months 9 hours ago) and read 5738 times:

Quoting zanl188 (Reply 23):
Quoting Starlionblue (Reply 22):

This is Tech Ops, please explain why the dip to enhance v-stab area.

Section 48 of the SP is structurally unchanged from a standard 747. Because of this the proceeding barrel section had to be recontoured, thus the dip. Please check the usual 747 books and sources for confirmation.

And I'm saying I was sure it was to increase area without adding too much height, but given the information you presented it turns out I was wrong.

I checked my book "Boeing 747 - Design and Development since 1969" by Guy Norris and Mark Wagner and you are indeed correct. The seemingly lower tail attachment is due to revised fuselage contouring. Boeing removed part of the tapered section so the tail sat lower.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlineJAAlbert From United States of America, joined Jan 2006, 1624 posts, RR: 1
Reply 25, posted (1 year 1 month 3 weeks 6 days 8 hours ago) and read 4384 times:

I recall reading somewhere that the MD-11's rudder was too small as initially designed and had to be enlarged. Is this correct? I also read that even as re-designed, some felt the rudder still wasn't sufficient. Anyone know more about this?

User currently offlineferpe From France, joined Nov 2010, 2805 posts, RR: 59
Reply 26, posted (1 year 1 month 3 weeks 5 days 16 hours ago) and read 4181 times:

Quoting JAAlbert (Reply 25):
I recall reading somewhere that the MD-11's rudder was too small as initially designed and had to be enlarged. Is this correct? I also read that even as re-designed, some felt the rudder still wasn't sufficient. Anyone know more about this?

I don't know about that, what I do know is that answer 4, that the structure below the tail engine serves no aerodynamical purpose is wrong. ALL vertical surfaces forward and aft of the CG serves to stabilize (aft) or un-stabilize (forward) the airframe in yaw so this part of the fin and even the fin engine nacelle are important parts of the directional stability of a MD11. The rudder is needed to increase the yawing moment when one engine goes inop. The aft stabilizing area can be reduced if one employes a yaw damper but the airplane must also be able to fly with an inop yaw damper and still be directionally stable (not dutch rolling to much).



Non French in France
User currently offlinePihero From France, joined Jan 2005, 4666 posts, RR: 77
Reply 27, posted (1 year 1 month 3 weeks 5 days 13 hours ago) and read 4110 times:
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Quoting zanl188 (Reply 3):
DC-10 & MD-11 rudders are double hinged. Makes them more effective than a conventional rudder of the same size.

In fact the main reason is to reduce at high speeds the rudder-induced rolling moment and the stress on a short-chord surface.

Quoting PITrules (Reply 2):
The engines on the L-1011 are further out on the wing than that of the DC-10. This would create more yaw during an engine failure on the L-1011 necessitating a larger rudder.

With respect, you have it backward : It's because of the greater yaw authority of the larger verttcal tail ande rudder that the engines could be placed farther away from the fuselage ( and the cabin )

Quoting md11sdf (Reply 4):
The structure that extends aft, below the rudder contains the aft mount/support for the number two engine.

... and its reverser.

Quoting PGNCS (Reply 9):
I can personally testify that the rudder on the L-1011 is EXTREMELY effective.

  



Contrail designer
User currently offlinePITrules From United States of America, joined Jun 2000, 3254 posts, RR: 6
Reply 28, posted (1 year 1 month 3 weeks 5 days 4 hours ago) and read 3886 times:

Quoting jetmech (Reply 6):
I was of the impression that it was the larger rudder itself that permitted the L1011's engines to be further out on the wing?

IIRC, the lower mounting of the L1011 centreline engine allowed for a rudder of much greater height. This in turn allowed the engines to be further out on the wing, the benefit of this being extra bending moment relief that ultimately provided the opportunity for a lighter wing structure.
Quoting Pihero (Reply 27):
With respect, you have it backward : It's because of the greater yaw authority of the larger verttcal tail ande rudder that the engines could be placed farther away from the fuselage ( and the cabin )

Seems like a bit of a Chicken/Egg argument. I can see advantages to having the engines further out (cabin noise, less wing bending, etc), and I see some advantages of having them closer in, such easier access for maintenance (closer to the ground), and less engine-out yaw requiring less rudder input equating to less drag.

Lockheed obviously thought one configuration was optimum, while McDD and Boeing (i.e. 737) thought having engines closer in was the way to go.



FLYi
User currently offlineStarlionblue From Greenland, joined Feb 2004, 17172 posts, RR: 66
Reply 29, posted (1 year 1 month 3 weeks 5 days 2 hours ago) and read 3859 times:

All things considered, I think that having the engines further out will win since it enables a lighter wing. The question is just how big you can make the rudder. 


"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinejetsetter1969 From Australia, joined Jul 2013, 57 posts, RR: 0
Reply 30, posted (1 year 1 month 3 weeks 5 days 1 hour ago) and read 3845 times:
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what about the depth of the tail fin? when comparing say the 744 and the 777 the 777 tail fin seens anorexic compared to the 747.

User currently offlineStarlionblue From Greenland, joined Feb 2004, 17172 posts, RR: 66
Reply 31, posted (1 year 1 month 3 weeks 5 days 1 hour ago) and read 3846 times:

Quoting jetsetter1969 (Reply 30):

what about the depth of the tail fin? when comparing say the 744 and the 777 the 777 tail fin seens anorexic compared to the 747.

It went on a diet. 

I think that's just a question of 25 years evolution in aerodynamics. More efficient with the same area. How they did it I have no idea.



"There are no stupid questions, but there are a lot of inquisitive idiots."
User currently offlinesturmovik From India, joined May 2007, 515 posts, RR: 0
Reply 32, posted (1 year 1 month 3 weeks 4 days 23 hours ago) and read 3804 times:

Quoting PITrules (Reply 28):
and Boeing (i.e. 737) thought having engines closer in was the way to go.

Having the engines further out on the wing also allows for greater fan diameter, provided the wing is dihedral. Of course, the designers of the 737 could not have foreseen that back then.



'What's it doing now?'
User currently offlinePihero From France, joined Jan 2005, 4666 posts, RR: 77
Reply 33, posted (1 year 1 month 3 weeks 4 days 23 hours ago) and read 3803 times:
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Quoting PITrules (Reply 28):
I see some advantages of having them closer in, such easier access for maintenance (closer to the ground), and less engine-out yaw requiring less rudder input equating to less drag.

1/- These pics reveal no significant difference between engine height, do they ?

View Large View Medium
Click here for bigger photo!

Photo © Justin Cederholm


View Large View Medium
Click here for bigger photo!

Photo © Nicholas Peterman



2/- The drag due to rudder is quite negligeable in the sum of all aerodynamic and thrust forces involved : around 1/15 th of the rudder -cum- vertical tailplane side "lift".

No, the #2 engine location decision caused the tailplane surface to be dimensioned so, hence the ideal engine location in that decision. Certainly not a chicken-and-egg argument.



Contrail designer
User currently offlineLH707330 From United States of America, joined Jun 2012, 848 posts, RR: 0
Reply 34, posted (1 year 1 month 3 weeks 4 days 8 hours ago) and read 3545 times:

Quoting Starlionblue (Reply 31):
More efficient with the same area. How they did it I have no idea.

The higher aspect fin and rudder certainly help, I suspect part of the consideration with the 747 was limiting total height. I can't think of a civil airliner with a lower aspect fin off the top of my head, even the DC-8 and 707 have fins shaped closer to the newer ones than the 747 does....


User currently offlineMax Q From United States of America, joined May 2001, 4778 posts, RR: 19
Reply 35, posted (1 year 1 month 3 weeks 4 days 5 hours ago) and read 3513 times:

Quoting jetsetter1969 (Reply 30):
what about the depth of the tail fin? when comparing say the 744 and the 777 the 777 tail fin seens anorexic compared to the 747.

It looks way too small and out of proportion to me, maybe something to do with the constant 'tail wag' of the -200 series ?
Don't know about the -300, never been on one.



I stand to be corrected but I believe the vertical stabilizer on the 747 is so large and effective that it can be dispatched with no yaw damper ?



Certainly couldn't do that on the B707 / 727 !



The best contribution to safety is a competent Pilot.
User currently online747classic From Netherlands, joined Aug 2009, 2214 posts, RR: 14
Reply 36, posted (1 year 1 month 3 weeks 3 days 20 hours ago) and read 3380 times:

Quoting Max Q (Reply 35):
I stand to be corrected but I believe the vertical stabilizer on the 747 is so large and effective that it can be dispatched with no yaw damper ?

On the 747 two yaw damper systems are installed (one for the upper rudder and one for the lower), one may be unservicable for dispatch.
Actually I have flown the 742 and 743 with both yaw dampers off during acceptance flights, performed after a D-check :
No dutch roll was noticed.

The max rudder deflection of the 747 classic series is 25 , at the 744 serie increased to 30, finally at the 748 series the lower rudder is made double hinged to cater for the further increase of installed engine thrust levels.(despite the increase in length of the 748)

Regarding the MD11 rudders the following : I remember that our company (KL) had troubles in the past with the initial operation of the MD11 out of SXM, with a wet runway.(and it rains a lot over there) and the availability of only full thrust TL tables for SXM.
Operating the 747 we always used full thrust T/O rolls (with packs off) towards the fast sloping terrain (hill) at the end of the runway. In case of an engine failure we could make it just right of the top of the hill. No problems with a wet runway.

The MD11 was not able to handle the combination of a relative low TOW, full thrust and a wet runway in an engine out situation in the low speed regime during the initial T/O roll ). Later special (reduced thrust) TL tables were used.

On the DC10 we didn't have the same problem (less installed thrust).

[Edited 2013-10-24 08:36:39]


Operating a twin over the ocean, you're always one engine failure from a total emergency.
User currently offlineKC135Hydraulics From United States of America, joined Nov 2012, 323 posts, RR: 0
Reply 37, posted (1 year 1 month 3 weeks 3 days 6 hours ago) and read 3204 times:

Quoting 747classic (Reply 36):
The MD11 was not able to handle the combination of a relative low TOW, full thrust and a wet runway in an engine out situation in the low speed regime during the initial T/O roll ). Later special (reduced thrust) TL tables were used

Was it due VMCG at these configurations being just too high to be safe?


User currently offlineMax Q From United States of America, joined May 2001, 4778 posts, RR: 19
Reply 38, posted (1 year 1 month 3 weeks 3 days 4 hours ago) and read 3185 times:

Quoting 747classic (Reply 36):


Quoting Max Q (Reply 35):
I stand to be corrected but I believe the vertical stabilizer on the 747 is so large and effective that it can be dispatched with no yaw damper ?

On the 747 two yaw damper systems are installed (one for the upper rudder and one for the lower), one may be unservicable for dispatch.
Actually I have flown the 742 and 743 with both yaw dampers off during acceptance flights, performed after a D-check :
No dutch roll was noticed.

Thanks 747Classic, always good to get the straight story from you.


Best wishes.



The best contribution to safety is a competent Pilot.
User currently online747classic From Netherlands, joined Aug 2009, 2214 posts, RR: 14
Reply 39, posted (1 year 1 month 3 weeks 2 days 23 hours ago) and read 3145 times:

Quoting KC135Hydraulics (Reply 37):
Was it due VMCG at these configurations being just too high to be safe?

Yes.

Remark : I never operated the MD11, but followed this embarrassing story after several intermediate stops of the then just introduced MD11 at SXM with many hours delay (until the runway was dry again) or the stop was sometimes even ommited at the AMS-SXM-CUR-AMS schedule.
Several SXM flight were actually flown with the 747 as a substitute, before the adapted MD11 TL tables (with reduced thrust) were made available for SXM.
At that time it was a nice subject to talk about with the MD11 crews at our carribean en route stations (underneath the palm trees with a nice cool beer.........that were the days), especially because we were the lucky ones not to operate " that aircraft with the mini DC10 tail ".

Nice climb-out profile of KL MD11 from SXM (low T/O weight , full thrust, high terrain in front of aircraft)

View Large View Medium
Click here for bigger photo!

Photo © Teemu Heikkonen



[Edited 2013-10-25 05:28:16]

[Edited 2013-10-25 05:29:25]


Operating a twin over the ocean, you're always one engine failure from a total emergency.
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