Local practice - ASI colour markings
 

I've been looking at the standard practices in lighter aeroplanes (that being my area) for airspeed indicator markings.

Part 23 and the lighter CS(JAR)-VLA require a green arc from Vs1 to Va (or other cautionary speed) where the amber arc starts. It also has a white arc from Vs0 to Vfe. Nothing radical about that.

But interestingly, CS.22 (the European glider and motorglider requirements) show the green arc starting at 1.1Vs1, and the white arc starting at 1.1Vs0 - effectively giving the pilot a 10% visual warning (should he/she/it be looking at the ASI anyway) of the level stall. Additionally, CS.22 fairly uniquely in light aircraft codes, requires a blue line at Vref, which again seems a sensible thing to do to me.

It strikes me that, at-least for these reasonably simple aeroplanes, the European Motorglider standard has taken a simple, but sensible, small safety measure.


Can anybody enlighten me on other local practices with regard to ASI marking, or for that matter opinions about what is best practice (within our outside of the various regulations that we all work with).

G

Have the glider & motorglider markings evolved because of the practice of thermalling at close to stall speed and they generally don't have flaps?

No idea I'm afraid, although for a while I sat on the committee responsible for those, that bit was set in stone before my involvement (and I'm no longer involved - in fact, post EASA, I'm not at-all sure who is!). But your argument about being close to Vs does make logical sense.

The presence, or not, or flaps wouldn't affect the bottom of the green arc would it?

G

I'm a glider pilot myself, with about 75 hours now.

In terms of ASI markings, the glider I usually fly (an unflapped 15m machine) has exactly one marking, which is a red line at VNE (135kts). VA (or whatever the max maneuvering acronym is) is 108kts, but isn't marked. Stall is ~38kts, while thermalling speed is 45-50kts. Cruise speed is lift-dependent, a varies from 55kts upwards.

The "full" set of markings typically seen in a glider instrumented in the last 5-10 years would be a green line from some factor above stall (1.2?) to max maneuving, then a yellow line to VNE, where there'd be a red line. There's usually a yellow "pointer" at best unballasted glide.

Some pilots of flapped gliders will put a ring round the ASI with markings for the "best" flap setting for each speed range, but this varies depending upon how much ballast is loaded.

To be honest, when flying my ship (which is not a grob103 despite my moniker) I only glance at the ASI occassionally - wind noise and control feel are much more important, and when cruising between thermals I have a vario to make annoying sounds at me to speed up or slow down.

I've got a good photo of a recently purchased glider panel layout if anyone's interested.

Flap setting will markedly affect stall speed.

Cheers,

David