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From: (Ed Hahn)
Subject: Re: causes of go 'rounds?
Date: 13 May 94 11:31:44

   Fred Christiansen ( wrote:
   : While driving past the PHX airport last Sunday, I observed an AmWest 737
   : descending to land and then pull up for a(n apparent) go 'round.  My
   : in-laws, who live fairly close to the airport, tell me that they see
   : go 'rounds from time to time (well, with greater frequency than I would
   : have tho't).

   : What are the reasons for which a pilot might decide to go 'round?
   : --
One reason I haven't seen mentioned yet on this thread is the
possibility that the aircraft in question may have been undergoing a
flight test, and that a go-around was part of the test protocol.
Admittedly, this is a very small chance, but PHX is AWE's maintenance

When I was working for the airlines, we were on a certification test
flight for a new GPWS for a DC10-30.  As part of the test flight, we
did a couple of go arounds at OKC, to test how the ground prox behaved
during the go around.

I should also mention as a side note that another part of the test
protocol was to descend at several thousand feet per minute at the
ground, wait until we got the most urgent warning, and pulled out of
the descent.  The minimum altitude we attained at the time was 700ft
AGL.  FYI, the PAI for the airline, DAR and DER for the
manufacturer, and other FAA personnel were onboard, and the entire
test plan was approved ahead of time.


////////   Ed Hahn | | (703) 883-5988   \\\\\\\\
The above comment reflects the opinions of the author, and does not
constitute endorsement or implied warranty by the MITRE Corporation.
Really, I wouldn't kid you about a thing like this.

Newsgroups: sci.aeronautics.airliners
Date: 17 Aug 97 15:41:08
From: kls@ohare.Chicago.COM (Karl Swartz)
Subject: Re: B747 technical questions

>>> The JT9D was flight tested
>>> on a B-52 and the RB.211 was flight tested on the port pylon of a
>>> VC-10.  How was the CF6 flight tested?  Perhaps on a C-5A, from whose
>>> TF-39 engines the CF6 was developed?  On what, then, were the TF-39
>>> engines flight tested?

>OK, maybe I'm being the Devil's Advocate here, but Why bother ?

>From 60 years of gas turbine flying, improved Simulated Facilities,
>improved mathematical modelling and suchlike, there is minimal info to
>be gleaned from flight testing in an unrepresentative environment.

If you're referring to the TF-39, it appeared in the 1960s.  There may
be 60 years of gas turbine flying now (actually more like 55), but much
of that experience didn't exist 30+ years ago, and the simulation
facilities were primitive compared to what exists today.  The TF-39
was the first high-bypass ratio turbofan, too, and probably 2.5 times
more powerful than any previous jet engine.

If you're talking about flight testing of engines in general, Boeing's
propulsion people and Pratt and Whitney felt that you were correct and
that flight testing the PW4084 (the first Pratt engine for the 777)
was not necessary.  It was a derivative of an existing, proven design,
and they had done extensive ground testing and simulation of it, so
they didn't expect to learn anything from flight testing.

Others in the 777 program generally accepted that position, but since
nobody had ever relied on ground test and simulation data alone, they
thought it would be wise to flight test the engine to prove that they
had in fact learned everything on the ground.  A sanity check, just
as they built a mockup of the 777's section 41 (the nose and cockpit
area) to validate the CAD tools, which were supposed to make mockups

On one of the first test flights (on the first 747), the PW4084 had a
compressor stall.  This turned out to be due to insufficient rigidity
in the fan housing.  At takeoff power, under high angle-of-attack, and
with a cross-wind, the fan housing ovalised too much and impacted the
fan blades.  It's a good thing they did go ahead with flight testing!

Karl Swartz	|Home
Moderator of sci.aeronautics.airliners -- Unix/network work pays the bills

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