742 > 743 shop mod

[barit1]

My recollection is 25 years ago 747-200 operators were given the choice of modding their ships to the SUD 747-300 via a kit. I believe only KLM elected to do so - but how many ships did they actually modify? Any pix in the shop?

[N707ZS]

I think there were 10 Dutch and 2 French UTA? 22514/5 machines.

I am quite sure there was a magazine article somewhere with photos of the new front end being lowered into positon.

[Groundloop]

Officially they did not become 747-300s. Their correct designation was 747-200SUD.

[WHBM]

Japan Air Lines also did a couple of 747-100 aircraft, which are now with Orient Thai.

Photos: Boeing 747-146B/SR/SUD Aircraft Pictures | Airliners.net (http://www.airliners.net/photo/Orient-Thai-Airlines/Boeing-747-146B-SR-SUD/1406814/M/)

I too recall a photo in Flight magazine at the time, shot from up in the hangar roof, of a KLM 747 with the modification section cut out and the new section about to be lowered in with an overhead crane.

It was a very substantial bit of work for what turned out to be a marginal increase in capacity. The control runs in the 747 from the flight deck go back through to the main cabin ceiling so all these had to be redone. It turned out cheaper to sell the aircraft and buy a new one, which is what carriers like Singapore actually did. Boeing of course were happier with this arrangement as well.

[Semu]

I am told that Boeing also offered a mod to shorten the upper deck as part of a pax to freight mod on the -300, to make it a more viable freighter (weight savings). Unless I am much mistaken, it has never been done.

There have been a number of other mods suggested for the whale. My favorite was a JAL request for a fixed gear version, for domestic use.

[barit1]

I recall the early Boeing studies on the SUD indicated that drag should be fractionally less than the -100/200 because of the area rule effect (http://en.wikipedia.org/wiki/Area_rule) (generally attributed to Whitcomb).

If one had access to -200 and -300 cruise control manuals, with same engines, running same weight and FL and SAT and Mn, we could see if this was realized. :)

[WHBM]

That comment about the drag reduction rings a bell as well from the time. If I recall correctly it all started with the 747SP development, where the shorter forward fuselage brought the rear taper of the upper deck bulge closer to the wing root (the forward fuselage was shortened but the bulge remained the same length) and gave an area rule benefit that way.

If you were to look at photographs of the 747SP and the 747-300 just in this area you would notice they looked the same. This drag reduction was stated to be another part of the 747-300 genesis, along with the capacity increase.Now I'm not an aerodynamicist so others can comment better.

It must be a very marginal benefit though because throughout the 747-300 production cycle the 747-200 continued to be manufactured and to sell. It was only when the 747-400 came along that both older models stopped production.

It also raises the question, if the drag reduction is noticeable, why when the 747-400 came along do the 747-400F freighter versions all have the old-style short upper deck.

[barit1]

I never thought of the 747SP involvement, but logically you are right.

Inasmuch as payload tonnage is the $$ in a freighter, and the SUD doesn't lend itself to easy loading (except for SLF), but adds empty weight & cost, I think there's valid reason to keep the short upper on a -400F.

[CV880]

Boeing initially confused the 743 drag issue and had to issue a correction to clarify their initial statement. If I recall the issue correctly the area rule effect of the lengthened upper deck actually caused a slight improvement in the drag curve (delayed the drag rise) so the -300 could go a bit faster before it got into the high drag regime but the greater wetted area actually increased drag overall so comparing an identical 742 and 743 on the same flight the 743 could get to a point a bit ahead of the 742 but the 742 could go a couple of hundred miles further than the 743 before running out of gas.
There were a few 743's converted to freighters (I know of Fedex and Dragonair) and the upper deck was unchanged externally. The internal structure and control runs were re-arranged aft of the upper deck doors to enable a 743 freighter to carry the same number of 10 FT high pallets as a 742.

[WHBM]

The 743 had better performance than the 742, and as they seem to have used the same engines I wonder how it was achieved. The first Singapore Airlines nonstops from London to Singapore started with the 743s arrival, obviating the refuelling stop in The Gulf.

Regarding the freighter conversions needing to have the longer upper deck rearranged and the floor cut back, I presume this is also taking place on the 747-400 freighter conversions we are now starting to see.

[Kitoro Kid]

B747-400F have short upper deck , as if they had 400 pax style upper deck you lose volume on main cargo deck . The currect 400F gives you more Q7 contour plts , as against Q6 plts. The 400 BCF has less maindeck volume than a factory build 400F because they keep the original upper deck , as well as only having a SCD , only benefit of having a BCF is better fuel burn over 200

[CV880]

WHBM,
Yes, the 747-400 BCF upper deck was structurally re-arranged in a similar manner to the 743 freighter conversion. Basically the aftmost floor beams behind the upper deck doors are removed, the fuselage frames strenghtened and tension ties installed (to hold the sides together) about 3 feet above where the floor beams used to be to allow 10 foot high pallets to be loaded in the same locations as on a 747-200 freighter. The control cables and aircon ducting was rerouted as well. On the 743 SF the upper deck aft partition was one window frame aft of the doors. On the 744BCF the partition was one or two frames further aft to allow a galley to be installed aft of the doors.
The 743SF used a standard 742 upper deck access ladder and location however the 744BCF used the 744F ladder arrangement which gives more flexibility to pallet loading on the main deck and takes up less room on the upper deck.
Re performance, I think all the SIA 743's had JT9D-7R4 engines which was the last and best of the JT9 line whereas their 742's had a mixture of earlier model JT9's ie. -7A, -7Q and this was the major performance enhancer on SIA's 743.