Green band on ASI

This may seem a little academic, but definition of the lower limit of the
green band on ASIs is inconsistent in places.

EASA Certification Specifications for Sailplanes and Powered Sailplanes, CS
22.1545 (Air-speed indicator): "Each air-speed indicator must show the
following markings: ... (c) for the normal operating range, a green arc
with the lower limit at 1.1 VS1 with maximum weight and for wing-flaps
neutral (see AMC 22.335) and landing gear retracted and the upper limit at
the rough-air speed VRA."

So far so good. Many people fly aircraft certified to CS22, or its
predecessor JAR22. The latter dating back to at least 1981. Even before
that, the lower limit of the green band should have set according to the
flight manual.

However, the FAA Glider Flying Handbook seems to be at variance. It says
(p4-5):

* The lower limit of the green arc — stalling speed with the wing flaps
and landing gear retracted.

Since there is little reason to fly at less than min sink, flying at stall
speed doesn't seem like the normal operating range.

On Fri, 21 Feb 2020 10:38:33 +0000, John McCullagh wrote:

This may seem a little academic, but definition of the lower limit of
the green band on ASIs is inconsistent in places.

EASA Certification Specifications for Sailplanes and Powered Sailplanes,
CS 22.1545 (Air-speed indicator): "Each air-speed indicator must show
the following markings: ... (c) for the normal operating range, a green
arc with the lower limit at 1.1 VS1 with maximum weight and for
wing-flaps neutral (see AMC 22.335) and landing gear retracted and the
upper limit at the rough-air speed VRA."

So far so good. Many people fly aircraft certified to CS22, or its
predecessor JAR22. The latter dating back to at least 1981. Even before
that, the lower limit of the green band should have set according to the
flight manual.

However, the FAA Glider Flying Handbook seems to be at variance. It says
(p4-5):

* The lower limit of the green arc — stalling speed with the wing flaps
and landing gear retracted.

Since there is little reason to fly at less than min sink, flying at
stall speed doesn't seem like the normal operating range.

Curiosity: why is this a problem unless you're shipping a glider from USA
to Europe or vice versa?

After all, FAA != EASA


--
Martin | martin at
Gregorie | gregorie dot org

The FAA Glider Flying Handbook is not a basis for aircraft certification. It is simply wrong here.

I sometimes fly at less than minimum sink speed, e.g., when flying in a
narrow area of weak wave.Â* Whereas the lower speed increases the sink
rate, the longer time in the lift plus the smaller turn radius, I
believe, improves my overall climb.Â* I could be wrong, of course.

On 2/21/2020 3:38 AM, John McCullagh wrote:
This may seem a little academic, but definition of the lower limit of the
green band on ASIs is inconsistent in places.

EASA Certification Specifications for Sailplanes and Powered Sailplanes, CS
22.1545 (Air-speed indicator): "Each air-speed indicator must show the
following markings: ... (c) for the normal operating range, a green arc
with the lower limit at 1.1 VS1 with maximum weight and for wing-flaps
neutral (see AMC 22.335) and landing gear retracted and the upper limit at
the rough-air speed VRA."

So far so good. Many people fly aircraft certified to CS22, or its
predecessor JAR22. The latter dating back to at least 1981. Even before
that, the lower limit of the green band should have set according to the
flight manual.

However, the FAA Glider Flying Handbook seems to be at variance. It says
(p4-5):

* The lower limit of the green arc � stalling speed with the wing flaps
and landing gear retracted.

Since there is little reason to fly at less than min sink, flying at stall
speed doesn't seem like the normal operating range.




--
Dan, 5J