R22 vs R44 Airspeed indicator. Why the difference?

[Haga Martins]

Hey helicopter pilots. I´ve been wondering this days, why is there a differcence between R22 and R44 airspeed indicator?
I mean, of course not the VNE speed, but why the green area in R22 starts at 50Kt and R44 and also R66 starts at 0kt.

I couldnt find such information reading the POH. Can someone explain me that?

[lelebebbel]

Originally Posted by Haga Martins

Hey helicopter pilots. I´ve been wondering this days, why is there a differcence between R22 and R44 airspeed indicator?
I mean, of course not the VNE speed, but why the green area in R22 starts at 50Kt and R44 and also R66 starts at 0kt.

I couldnt find such information reading the POH. Can someone explain me that?

You may have to ask Robinson that question. My best guess has always been that especially the early versions of the R22 (prior to the Beta) had very marginal OGE hover performance, and also terrible characteristics for engine-off landings. Additional factors were the manual throttle control, and the fact that an R22 is essentially always flying at MTOW.
Marking the airspeed indicator as such, may have been an attempt to make people more or less consciously stay above 50KIAS to increase safety margins, even if there isn't a specific flight manual limitation that would prevent them from flying slower. Once certified with these markings, there would've been little motivation to change them, even if later Beta and Beta II models improved margins by a little bit.

The R44 and R66 are much closer to most other helicopters when it comes to those metrics.

[SFIM]

My understanding is that the R22 only has 1 static port; so the airspeed indicator is not considered accurate until you get to 50kts; whereas the R44 and R66 have 2 static points and it’s considered to be accurate as soon as it starts indicating.

[lelebebbel]

That's an interesting theory. However the airspeed calibration chart starts at ~28kts in the R22, and around 18-20kts in the R44 and R66. So if that was the case, shouldn't the indicator be marked accordingly?

[SFIM]

The airspeed calibration curve in the R22 POH, doesn’t actually names the Axes so it can’t be seen which is the “indicated” and which is the “calibrated” , wheras for the R44 / R66 they are named.

re your bigger question, I don’t know