SAA-SAL From Belgium, joined Nov 2000, 356 posts, RR: 3 Posted (11 years 7 months 1 week 2 days 20 hours ago) and read 2466 times:
I often hear of comments on this forum of people saying that a certain aircraft has bad performance because it is getting old when new aircraft of the same model are still coming off the production line. The best examples concern A340 "classics" and the B767 family. So here is my question : do aircraft loose performance with age. I can imagine a 1% change during an aircrafts' life but surely no more? Do this really justify replacing them with very expensive newer aircraft?
Douglas DC-9 From United States of America, joined Sep 2001, 303 posts, RR: 2
Reply 2, posted (11 years 7 months 1 week 2 days 20 hours ago) and read 2427 times:
It all depends on what kind of aircraft it is and how often it is used, as well as what type of weather climate it normally flys into. For example, if it flys in cooler weather the aircraft may have waterlines freeze up.
CitationJet From United States of America, joined Mar 2003, 2469 posts, RR: 3
Reply 4, posted (11 years 7 months 1 week 2 days 18 hours ago) and read 2363 times:
I know that the B-52 cannot achieve some of the original performance specs (speed, altitude, etc) because of additional antennas, radomes added that increases drag. Also the skin is wrinkled forward of the wing.
Boeing Flown: 701,702,703;717;720;721,722;731,732,733,734,735,737,738,739;741,742,743,744,747SP;752,753;762,763;772,773.
MD88Captain From United States of America, joined Nov 2001, 1338 posts, RR: 20
Reply 5, posted (11 years 7 months 1 week 2 days 18 hours ago) and read 2343 times:
Absolutely, aircraft lose performance with age. Any aircraft. Many things contribute to degraded performance like:
1. Aircraft get bent. Hard landings, turbulence, high G manuvers, and many other things mean that an aircraft becomes slightly bent. Very few aircraft trim exactly the same, and some require really weird trim like 3.5 units right rudder trim and 1 unit left aileron. Original performance specs are done on straight, new aircraft without the added drag of a twisted airframe.
2. Aircraft get lumpy. Check out the doublers and extra rivets on older aircraft. Check out the patches on leading edges. The orginal, new aircraft came from the manufacter with nice smooth skin. Lumps mean more drag,
3. Aircraft get bumpy. Old aircraft are covered in little dents. Dents small enough that they don't require repair. Bumps mean more drag and higher fuel burn.
4. Aircraft get out of trim. The rigging on flight control surfaces can get out of spec after awhile meaning that a level yoke may give you less that level flight. Agin you end up flying slightly out of trim and thus increase drag.
5. Aircraft get fat. They get heavier over the years with an accumulation of dirt, grease, and stuff. Spilled cokes, peanuts, tools (mechs leave them often), and just little bits of crap. The older the aircraft the heavier it gets. Only the original W&B is going to be accurate.
6. Aircraft get tired. Specifically engines get tired. The closer they get to overhaul the more worn they get and the less thrust they produce.