Airspeed reads Low

[uiJCKftERAh]

At cruise (160mph), the IAS reads 128mph. At pattern speed (80), the IAS reads 75, and this is true all the way down to the runway. Stall speed seems about right, 49 clean and 41 flaps down. Pitot leak? Thx Rolly9

 

[dynonsupport]

Where is your static connected and how does your altitude compare to something like GPS?

 

[PilotKris]

Sounds like another case of Static Source Position Error.

 

[dynonsupport]

Also, check that you have the EFIS's speed units set to the units you're expecting. It can be set to knots, mph, and kph. It under SETUP>UNITS.

 

[uiJCKftERAh]

This is an RV-9. Static source is on both sides between cockpit and tail. I would think if the A/S is low, I have a Pitot leak or partial block.

 

[uiJCKftERAh]

Also the GPS altitude and the EFIS agree. But the pitch is not right.
RC

 

[khorton]

This is an RV-9.  Static source is on both sides between cockpit and tail.  I would think if the A/S is low, I have a Pitot leak or partial block.  

What were the results of your pitot leak check?  A static system leak check is also a good idea.

GPS altitude and barometric altitude should be similar at very low altitude, but they may differ substantially at higher altitudes.  At what altitude above ground did the EFIS and GPS altitude agree?  

What do you mean by "the pitch is not right"?  Is the displayed pitch attitude in error by a constant amount, or does the displayed pitch attitude change strangely when you accelerate or decelerate?

 

[aubreypric]

At cruise (160mph), the IAS reads 128mph.  At pattern speed (80), the IAS reads 75, and this is true all the way down to the runway.  Stall speed seems about right, 49 clean and 41 flaps down.  Pitot leak?  Thx Rolly9

I had this problem on my RV. Airspeed low and altitude low. It was the placment of the static port. I solved it by putting a small dam in front of the static ports. It wasn't my idea. Van's told me what to do. It works.

 

[khorton]

At cruise (160mph), the IAS reads 128mph.  At pattern speed (80), the IAS reads 75, and this is true all the way down to the runway.  Stall speed seems about right, 49 clean and 41 flaps down.  Pitot leak?  Thx Rolly9

I had this problem on my RV. Airspeed low and altitude low. It was the placment of the static port. I solved it by putting a small dam in front of the static ports. It wasn't my idea. Van's told me what to do. It works.

It looks like you had a problem with static source position error (i.e. the static port was at a position were the pressure was not the same as the free stream static pressure).  The dam in front of your static port changed the pressure at the port.  Static source position error can be measured with a combination of ground and flight testing.  Lots more info here.