747-400 sans winglets

[jb2_86_uk]

sorry, this is my second thread on the 744 this week!

Are there variations of the 747-400 out there without the characteristic winglets?

I ask, after seeing this picture:
http://www.airliners.net/photo/Japan-Airlines---JAL/Boeing-747-446D/1015803/L/

I thought it may have been the information entered wrong by the photographer, but following a search for more pictures of this specific aircraft, all the results show the same aircraft without winglets, but still identified as a 747-446D. (I understand the final '46D' refers to the Boeing customer code? in this case JAL.)

Replies appreciated as always :ok:

JB

[Wizofoz]

Yes , the Japanese have a winglet-less, shoter range 747-400. I believe the reason for leaving the winglets off was for increased spar life in high-cycle operations.

the Japanese have had a couple of specialist 747s, they had a short range, high dnsity vertion of the -300 as well.

[jb2_86_uk]

Thanks wiz!

Now that you mention it, I think i remember reading about high density 747s for JALs domestic/short range routes some time ago!

JB

[sinkingship]

Yes, you are correct the digits after the series number relate Boeings customer code.

[aviate1138]

I travelled from Tokyo to Osaka in one. The winglets were missing and the seat pitch felt like it was 23" or less! :rolleyes: Actually about 28" I think. Being over 6 feet didn't help! Returned on the Bullet train (Shinkansen)

[flite idol]

I believe the "D" stands for domestic! Built for short distance high density Japanese markets.

[OutOfRunWay]

Them thar winglets only give you a significant fuel saving at cruise speeds and altitudes where the induced drag is reduced by them. On the detrimental side you have to cart the winglets up to that altitude first, and each weighs in at a couple of hundred kilos.

So: for short hops, the cost of bringing the winglets up to cruise level will outweigh the cost saved in the short cruise phase of the flight.


Regards, OORW

[Spanner Turner]

On the detrimental side you have to cart the winglets up to that altitude first, and each weighs in at a couple of hundred kilos.

Yes, they aren't fitted to the -D's due to minimal time in cruise on the JAL/ANA domestic sectors however, they're really not heavy at all. My airline has a habit of damaging -400 winglets on a fairly regular basis and they're very light and easy to get on and off - they're mainly made from fibreglass. An easy two person job.


From the Maintenance Manual:



Winglet

The Winglet is a drag reducing component which attaches to the
Wing Tip Extension at two fittings with three bolts. The construction
of the Winglet follows standard airfoil practices using a structure of
spars and ribs enclosed by skin. The majority of the Winglet Skin is
made of composite material except for the Leading Edge and Tip
which uses sheet aluminum. The Winglet is faired into the Wing Tip
Extension with three fairings and weighs about 146 lbs.



That's around 65 - 70 KGS

:ok:

[OutOfRunWay]

that light! Im impressed - those things are quite large :ok:

Slightly off-topic, does anyone know if you are allowd to dispatch a 744 with on or both winglets missing?

OORW

[mutt]

Dispatch with 1 = Permitted
Dispatch with 0 = Not Permitted


Mutt

[World of Tweed]

A Standard 744 is permitted to dispatch without a winglet but there is a penalty on MTOW. I think its in the region of 1000kg.

As for winglet weight - well the airfoils themselves might only be 70kgs but the structural weight added to strengthen the outer main spar to cope with the winglets bending moment is likely to be considerably more.

As I understand it the JAL/ANA 744Ds were constructed with the standard structure so that after serving half their life in the high-cycle but low hours shuttle operation they could be converted to a Longhaul config to use the remaining hours with the relatively low cycles associated with long haul travel.

Another point of interest is that to preserve the cycles on the landing gear most of the shuttle flying around Japan is done with the gear down.

[flite idol]

Surely cycles on the gear refers to take-off/landing cycles not extend/retract cycles?

[OutOfRunWay]

Flying with the gear down??? All the time????

Are you sure? My thinking would be that for the extra fuel costs of flying with the gear down, they could pack the entire hold with winglets.:8

I remember reading somewhere that the gear has been strenghtened for all those extra cycles flying short haul.

regards, OORW

[World of Tweed]

I can't remember the exact sector length but there was a cut off as to when they would retract the gear and when they wouldn't bother.

Actually the gear is probably not strictly required to be as strong as its longhaul partner if Boeing wanted to recertify them. Think about it....Much lower average takeoff but similar landing weights to the Longhaul variant. I believe the gear was probably optimised for short sectors - main issue here is brake temperatures as with frequent short turnarounds you still need the brakes to be cool enough for a max energy RTO on the next takeoff.

A Landing gear cycle is not defined with a landing/take off its is derived from Extension and Retraction. I.e. the landing gear mechanism being "cycled".

This is circa 2003 info as thats when I worked in Tech Services. They may well have changed the the policy by now but the Gear overhaul is an expensive cycle driven procedure. Any increased fuel burn on a short sector
will be offset by the reduction in frequency of Gear overhauls.

The specific 'numbers' will all be in some spread sheet somewhere which will examine the pros and cons of with/without winglets, with/without gear down etc. All to find the most "Financially Efficient" - not necessarily fuel efficient - way to operate the aircraft on any given route.

[KiloB]

Would it be fair comment that winglet design seems to be a far from mature technique. Just compare the 320 & 737 versions (for two A/C in the same weight/performance cat). If the designers have the same goal, they sure are using different methods!

[Oftenfly]

Hmm. I think the "winglets" on an A320 work on a somewhat different aerodynamic principle, and tend to be referred to as "wingtip fences".

[airfoilmod]

320: upper facet-winglet
lower facet-fence

Winglets can be tuned for Climb or Cruise, or a combination, but declining performance as a combo. The Structure limiting factor is the wing root and outer Spar (Flex.) and adds much more weight than the winglet itself.

Airfoil