Date: 6/3/2004 2:05 PM Central Daylight Time
Message-id:

Time to time I come across fighter aircraft instrument panel photographic
images and find no red line limit on the airspeed indicator.

Look at the airspeed indicator. If there is a second pointer painted like a
black and white barber pole there is usually no need for range marks. There is
a little bitty black pointer at roughly the 7 o'clock position that is adjusted
by a screw on the back of the indicator (the pointer probably doesn't show in
any picture you have). This sets the mach limit. The barber pole is what the
pilot sees as maximum airspeed. The barber pole changes as a function of
altitude.

What is the
policy and who puts the red line on the airspeed indicator?

I can only speak for the USAF. The ground troops install the line. It's called
a range mark. In avionics I installed them. Look on engine instruments,
G-meters, hydraulic gauges etc and you will see an assortment of arcs and
lines. Red lines indicate do "not excede" (example 104% on F-4E tachometers
IIRC), red arcs indicate a danger range (pressure gauges sometimes have them),
yellow indicates cautions, green indicates safe or proper function range and
blue indicates auto lean on recips. When you look at all range marked
indicators you will also see a white line. This is called a "slippage mark"
which indicates movement of the cover glass if it occurs. the slippage marks
are put in the r o'clock position unless it would blend in with or obscure the
scale in which case it is placed in a blank area of the scale. We usually used
white nail polish or paint for the slippage marks. The range marks are self
adhesive paper or vinyl which we would cover with clear nail polish to extend
the life of the range marks.

Do red line
speed change depending on aircraft loading?

On F-4Es the G-meter had two sets of red lines. One was for clean the other was
if there were external stores IIRC.

Do they rub it off for secrecy?
Is it done at the factory?

I have seen factory range marks on indicators for civil aircraft usually
directly painted on the scale. I don't recall seeing any on USAF aircraft other
than indicators built in to comm/nav equipment.


For example I have Bf109E photo instrument panel with red line at 400 kmh.
The specification for Bf109E doesn't tell you what the red line speed is.

Emilio.

Dan, U.S. Air Force, retired