Bye bye 747

One of the design requirements of the competition was a ground level loading capability for heavy equipment like tanks and large vehicles. That meant a shoulder mounted wing, fuselage mounted landing gear to achieve the low stance of the airplane. The 747 was initially a passenger plane with heavy cargo adaptations, like the nose loading capability. But this requires an elevated loader that the C-5 doesn't require. In two competitions for military freighters, C-141 and C-5, Lockheed won both on " superior" management and budget plans. I have heard good comments about the C-141 but none re the C-5. I have examined the C-17 and THAT is a beautifully done and clever airplane. I hear lots of favorable comments from crews.

 

The C-141 was a very good airplane. It was still a mistake to go with the C-5, the squatting capability was unreliable, the entire plane was unreliable and the oversized pallets took time to break down in order for the C-130, and C-141 to deliver the cargo down range. That was one of the reasons the C-17 was built, and it is one hell of an airplane. Going back to the competition requirements, from what I understand, there was also a requirement for the aircraft to be able to land in the field, and I could not see a C-5 land on a makeshift runway.

 

I would think the 747 would make a good air cargo aircraft.
With UPS retiring their fleet of DC-8s (built like a brit shick house) there has to be a gap.

 

That doesn't sound right to me. The airplane has been close to Mach 1, I am told, but i have no knowledge of any differences between the nose and the wings. The sweepback is almost 38 deg. at the 1/4 chord and planform taper would add some more so I would think that it would do okay aerodynamically and structurally. I will see what I can find out.

 

There are active programs for the conversion of 747s from passenger to full freighters. This is a normal after life for a lot of airliner models after they are no longer fly passengers. Cargo is not impressed by new and pretty.

 

The C5 problems may have a lot more to do with requirements from the government's requirements than a fundamental flaw of Lockheed. Remember in the day hearing Lockheed complain that the C5 suffered from endless requirement changes from the government.

 

I believe their cruise can be right under the mach number. .98 or so.

 

That could be some of the cases, but it was an all around hydraulic and fuel systems nightmare. Also the nitrogen inerting systems would leak, or the liquid nitrogen that was vented out would freeze the sealant in the ribs located in the dry bays and cause more fuel leaks. The fuel quantity system was lousy, always replacing quantity harnesses. There weren't many systems on the C-5 in the case that if they were inop you could still fly the aircraft. KC-10, C-17, more than likely the 747 are able to still fly with multiple systems inop.

 

It's usually the engines which can't take the supersonic flow. Solofast would be the authority on that one.

 

I remember an interview with, I believe the Pres or CEO of Lockheed many years ago about government paperwork and red tape. He said the proposal for the 130 was carried to DC in a brief case and the proposal for the C5 was carried in a 130.

 

I remember my first ride in a 747. I still remember clearly the take off roll thinking "holy crap, how do they get something this big to accelerate this hard".

 

I wouldn't doubt that comment re the massive size of the C-5 proposal. i recall someone telling me that Boeing ordered a freight car of paper to print their C-5 proposal. Governmental changes were never ending and counter to achieving any rhythm in a design. Iv'e seen it.

 

I have flown on the A380 a couple of times and thought exactly the opposite. Slow to accelerate and I think the longest take off roll I have ever experienced! On approach it seems to wallow - strange feeling. The 747 is truly a wonderful aircraft and is one of the greats in aviation.

 

I remember sitting in the old parking zone along MIA's south perimeter road and watching 747s accelerate down runway 9R and usually unstick right in front of me. It was hard to believe that an object that big could actually fly!

As for the C-5, they have had issues, but I understand that the rebuilt C-5M's, with new wing center boxes, modern avionics and new engines, have been much more reliable. They're certainly a lot quieter!

 

Yes and no. The -200 and -100 747 freighters, which were all converted passenger planes, are all but done in the US market. The -400BCF's (Boeing Converted Freighter) are also seeing a lot less demand. My current employer retired the last of their BCFs last year, so we're all -400F and -8F on the 747 side. I can think of only one US operator that is still flying the BCF and that was my prior employer. I do agree, and hope, that their will always be demand for the nose loading capabilities of the 747 to carry outsize cargo but that is definitely more of a niche market. The 777F seems to be the hot ticket right now for standard palletized or parcel type cargo that is time critical.

 

I sat in the upper deck over the wing...and on both flights, I swear the second the wheels left the ground, it sounded like an old creaking ship as those wings flexed under all the weight. Both flights. Maybe it's in my head, but never heard a plane sound like that. Makes me think "no wonder they have wing spar problems"

 

I've been flying commercial for 30 years, and finally flew on a 747 this January for the first time.

Air France from GIG-CDG.......

Odd that.

 

I have noticed in video footage that the airframe is quite flexible in landing and take off sequences. There has to be some flexibility but too much over the long run can be a problem.

 

The aero guru said that the 747 airframe would survive M-1 but to reach and exceed it, a shallow dive would be required. No problem with the nose or anything else. Don is correct that engine inlet flow would be affected.

 

Bob thanks for the feedback. Read a book on 747 years ago which claimed that the front end had aero for over mach 1 as that is just the way it came out. That the head of Boeing told the designers the whole key to the plane would be in the wing, which was the real magic of the 747. Pus the whole task of designing and building it put boeing to the wall financialy.

Slightly off topic but didint a few of those turbofan 727's go over mach 1 in inavertant dives? You still see them all over africa, I think the 727 is replacing the DC4 as the tramp steamer of the skys in places where big loads out of poor fields is an asset, seen them on had packed dirt..

 

The 727 was designed to operate from short unequipped fields. The extreme high lift system was designed to allow the airplane to take off from short fields , attain cruising altitude and fast speeds, and land at short fields. The airplane has a rugged landing gear and great brakes and an aft air stair that provides loading and unloading when fancy equipment isn't available, so it is fulfilling its original design objectives at those outland dirt fields.That technology was transferred to the 747 with a wing that closely resembled the 727. It didn't have the triple slotted flaps but the rest of the high lift system was used with leading edge slats and a double slotted trailing edge flap. The wing geometry was very close and very efficient, especially when they applied the variable camber Kruger slat to the leading edge system. Both airplanes are examples of over the top aerodynamic excellence in wing design. I am fortunate to have been able to work on both of them.

 

The 727 wing.
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I know that early in its life, a DC-8 exceeded Mach 1 in a shallow dive. I haven't heard of any other subsonic airliners doing likewise.

 

I have been told that a Convair 990 did also, but I'm doubtful... cannot find any written evidence anywhere that it actually happened.

I'm assuming that the DC-8 is still the only 'subsonic' airliner to exceed Mach 1; it was certainly the first.

 

A Pan Am 707-121 exceeded M1 over Gander. It entered a spiral dive and by calculations attained Mach 1.3. It sustained damage in the pullout from a dive that started at 33,000 and ended at 7,000 ft. Secondary structure like fairings and access panels left the airplane and the wing reaching the yield point had a permanent increase in dihedral (but no fuel leaks). The horiz. stabilizer had to be replaced. Correct me if my figures are a little off. I'm digging through a bit of brain clutter.. Anyway, the airplane was put back in service. I forgot to mention that this incident occurred when everybody was out of touch with the instrument panel and no one noticed that the autopilot circuit breaker had popped and the Mach warning light was blinking. The pilot was in the cabin visiting the Pan Am VP of Atlantic Operations. The copilot was working some kind of paper problem and the airplane entered Mach tuck and started down.