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Do identical aircraft behave the same?

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Do identical aircraft behave the same?

Old 14th Oct 2012, 01:53
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Do identical aircraft behave the same?

Always wondered if two indentical triples or any other jets,behave the same?Are there subtle differences between the same planes?Do pilots prefer one 777 to another?In my profession,two identical maschines never behave the same,so how is it with jets?
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Old 14th Oct 2012, 03:41
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There are differences, even in ones straight out of the factory. But less so in fly by wire aircraft where the artificial stability of the control systems usually blend out the differences.
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Old 14th Oct 2012, 14:05
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Do you mean different models? A 767-200 vs. a 767-300? A 777-200 vs. a 777-300ER or 777-200LR?
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Old 14th Oct 2012, 14:46
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Do you mean different models? A 767-200 vs. a 767-300? A 777-200 vs. a 777-300ER or 777-200LR?
I think he means identically built aircraft; one that rolled out of the factory this month versus the last.....
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Old 14th Oct 2012, 16:05
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From an engineers point of view you always get the one that was built on a Friday afternoon & gives you s-- t even on a good day.
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Old 14th Oct 2012, 17:16
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From an engineers point of view you always get the one that was built on a Friday afternoon & gives you s-- t even on a good day.
I recall at BA we had at least a couple of Tridents that either couldn't cruise as fast as their stablemates or flew one wing low.
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Old 14th Oct 2012, 17:31
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Then there was the DC4 or 6 or some-such, that after hours of circuit work asked if they could fly around the circuit in the opposite direction, cos the flight engineer said he could see a curve in the fuselage.


Apocryphal? It was a story that hung around for years.
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Old 14th Oct 2012, 17:31
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Probably bent like X-ray Mike Dave
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Old 14th Oct 2012, 17:32
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Can't comment on FBW aircraft but whilst all a/c have very tight "interchangeability" limits 9which allows one part from an aircraft to be replaced by another from stock - unlike hand made cars) they are all different. Look at the weights and no two are the same (and this changes through an aircrafts life). Some will need different amounts of trim ...have better climb performance etc.
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Old 14th Oct 2012, 22:36
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I think he means identically built aircraft; one that rolled out of the factory this month versus the last.....
You nailed it,now how about FBW aircraft like the E-Jets,777 series,Airbus family etc?I fly on a 195 pretty often,same airline,same plane,similar weather but some of the jets just feel rougher or it maybe just a beginner pilot.lol!
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Old 14th Oct 2012, 23:14
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We have four A300s that were built within two years. They are almost the identical spec but each has its own character. I suppose it comes down to how he artificial feel has been set up and how each airframe has been used or abused over the years.
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Old 15th Oct 2012, 10:12
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I flew two 727-200's which were externally pretty much the same although they did have different hushkits. One was a bit of a dog compared to the other.

Last edited by JammedStab; 15th Oct 2012 at 10:14.
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Old 15th Oct 2012, 10:18
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I fly a fleet of brand new 738s. I can almost tell which possible registrations I am sitting in by the seat position. For the same index, some aircraft are perceptibly a little forward, back, higher or lower. Also I know in which aircraft the toilet seat stays up Other than that, they feel and fly pretty much identically.
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Old 15th Oct 2012, 10:38
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A320

Regarding to my feelins the A320-21X and A320-23X behavior quietly differs during landing. I believe one of the reasons may be different flap extension degrees in config FULL
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Old 15th Oct 2012, 15:44
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Computer monitors produced in a same company, same model, same time with the exact spec have color differences So i heard Color sensitive assignments do have minimum of 3 monitors manufactured in same brand, same company, same plant, same time and with same machinery and located in same location!

i guess it's a relative thing to compare as how far you expect any sort of two identical machines to behave, it may differ it's behavioral characteristics with age: the way they fly, way they being looked after, climate, etc

I assume two similar models with same specs, one flying in a tropical weather and other flying in far arctic will eventually have two different destinies with different characteristics of flying!

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Old 15th Oct 2012, 17:05
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MD80s when the same is not...........

any other jets,behave the same?Are there subtle differences between the same planes?


I do not have the privilege of flying 777s so I can not comment on that model.

I fly 737-NGs from my vantage point; provided the same model are compared at the same weight and density altitude then yes they do behave and fly the same. I am unable to tell the difference between one jet and another. I do have a “favorite” aircraft in the fleet, and think it “feels” great to fly but I suspect my evaluation is purely subjective and emotional.

If you try and compare different versions of the same jet, then no they are not and do not "fly" the same. The smaller lighter 737-700 will feel and fly quite differently than the 737-800 or -900.

I spent a dozen years flying the MD-80. That jet was unusual and I would say that two MD-80s built next to each other on the assembly line in a few years could feel and fly very differently, it was the strangest thing.

The MD-80 series jet manipulates its flight controls with a byzantine series of cables and trim tabs rather than hydraulic or fly by wire systems (affectionately knows as the Long Beach Cable Car {manufactured at Long Beach California}). Because the cables wear and stretch differently each aircraft develops it own unique feel. It was also by far the most difficult aircraft I have ever flown to get a smooth landing out of. Every time I thought I had it figured out, I would embarrass myself.
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Old 15th Oct 2012, 23:51
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Thanks for all your replies,very interesting read
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Old 16th Oct 2012, 02:18
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Doing the flight control checks you'll sometimes notice the controls are slightly freer, or stiffer, than typical. Minor difference.

The non FBW a/c typically have to be trimmed, primarily rudder. Sometimes it's slightly right, sometimes slightly left. Some use the same trim setting at different speeds and some need retrimming as the airplane slows or accelerates.

Engines can have slightly different spool characteristics, especially off of idle.

Small differences, sometimes noticeable. Probably no different than if you drove 20 different cars of the same make and model, especially if they're 5, 10, or 15 yrs old and well maintained. They'd be the same, but not 100% the same.
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Old 16th Oct 2012, 03:11
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All identical aircraft fly exactly the same.

The thing is, there are no aircraft which are truly identical.
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Old 16th Oct 2012, 10:40
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I know that EE Lightnings had differing characteristics
I never noticed any, unless you are talking about different marks.
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