IAS variation

[couleeone]

It is worthy to finally get around to note that when the windows, doors and vents are open my IAS lowers by 5-7 mph!

Try it, set up a cruise speed that allows windows and door to be open and watch as you open the vents it drops, then you open a window and it drops again with both windows and door...sort of incrementally. This became really apparent here in AZ when everything is opened up most of the time!

At first I thought the heat/density altitude was really affecting my airspeed and it does but the above is a direct correlation to the change in static pressure in the cockpit.


Air speed in the pattern is very important so be aware of the discrepancy!

Any thoughts?

Geo
www.cubdriving.com

[Jason Tepool]

You create much more drag with everything open, I've seen that here too with IAS and groundspeed.

[randylervold]

The back of your airspeed indicator is the static port so when you open the window you are changing the air pressure in the cockpit and thus the static pressure. IAS = difference between pitot and static pressures.

[Teamomm]

So what about maneuvering speed? Are you at 93 open or shut? And you are now on notice Geo to stop entering the pattern inverted. Tom

[couleeone]

Open or shut doesn't affect the ground speed, yes there is some drag but not noticeable in the GPS ground speed to me at least. I think at maneuvering speed and above it is unlikely the windows will stay open and your just not configures for high speed cruising. However the being vents open will affect the IAS.

Just so you know there is a difference in IAS when opened up and I believe its in your favor by indicating a few mph less. Just keep in tune with your senses.

Tom, I don't think being inverted changes my IAS but I sure will look to verify the next time I am inverted in the pattern! trouble is I am so busy pumping the primer keeping the engine running that I don't have much time to look other than out the skylight!!! You have much more experience at that than I do!!!! (LOL)