What Are Those "CUPS"....During Test Flights?

Sat Nov 20, 1999 1:54 am

Hey Aviators  ,
I was always wondering about the test flights. I noticed that all of the planes durning test flights have this "cup" thingy that they drag behind them on the vertical stablilizer or tail and at the cone at the end of the plane. What is that used for? Does it help show something? Can I have some explanations?   Thanks!

Simon Oh yea, Where can I get some kind of subscription to a magazine about Airlines and Boeing and Airbus.......etc.
Posts: 834
Joined: Sun Oct 24, 1999 9:03 pm

Airliners And Airways.

Sat Nov 20, 1999 3:25 am

The two major mags would be Airliners ( and Airways (

Hope that helps,


PS: Sorry, I am clueless on the "cups" you mentioned. For your sake, I hope Buff reads your question. I bet you ten bucks he has the answer. ;-)

RE: What Are Those

Sat Nov 20, 1999 5:29 am

About the "cone" you asked, I think you are talking about the protection of the tailsection in minimum take-off speed tests. Refer to this quote that I posted earlier and it describes what kind of test it is used for. It is basically used for fuselage protection.

Various tests are performed
for this condition for any aircraft in the world. This falls into a major
category of the so-called "test-flights", and in this case the testing is
being in regard to the resistance of this occurence to the aft fuselage
of the aircraft. The aircraft takes-off at the minimum possible
speed(kts-relevant to aircraft conversion) until the tailcone section
physically touches the runway, creating large amounts of friction.
However, the cone section is protected for testing purposes with specific
resistive materials. During the test, the aircraft produce enough speed
to rotate and create an enormous positive angle of attack, but does not
generate enough lift force to take-off until the very last stages of V2.
Until then performance will be recorded in various ways and data must be
carefully analyzed so that errors will not happen in a case like this.

Basically it is attached to the tailsection to prevent it from touching the rwy. and damaging.

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RE: What Are Those

Sat Nov 20, 1999 6:19 am

Those cones that are trailed behind the tail of the plane are used to measure ambient air pressure so that all measurements of air pressure throughout the plane can be measured against the ambient pressure.

The thing attached under the tail section during maximum rotation tests are called tail skids and keep the tail section from being dammaged.


RE: What Are Those "CUPS"....During Test Flights?

Sun Nov 21, 1999 8:02 pm

In order to calibrate the airspeed indicator and altimeter of an aircraft it is necessary to know the static pressure of the air at the altitude the aircraft is flying. A line is trailed behind the aircraft long enough to measure the static pressure of 'free air' - in theory, unaffected by the aircraft itself. The 'cup' you mention is called a 'trailing static cone', and its purpose is to stabilise the pressure line behind the aircraft.

The static pressure measured at the trailing line is compared with that measured on the aircraft (by its pitot-static tubes or static ports on the fuselage side) in order to carry out the calibration. The same calibration is then applied to other aircraft of the same type.

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