Inaccurate Airspeed & No Gear Unsafe Light

[HaldenG]

I recently purchased a 231 and am having a few issues.  I'm going to have them checked out by my mechanic but I thought I'd put them up on here to see if anyone has seen something similar or can give any advice on areas to look for problems.

 

My airspeed indicator shows 40 KTS at rest on the ground and also shows about 20 KTS difference when compared to the GPS at low altitude with negligible winds.  My altimeter and VSI seem to be acting correctly and there was an IFR pitot static inspection done about 2 months ago.  Additionally when I took off yesterday, there was a delay in gear retraction and the warning horn came on as if I had not reached the required speed to override the airspeed safety switch and allow for gear retraction (I was approximately 300' AGL showing just over 100 KTS on the GPS).  My Gear Unsafe light tests good but never comes on - both floor and panel Gear Down lights work fine.

 

Suspected problems:

1. Obstructed Pitot Tube/Line

2. Bad Airspeed Indicator requiring overhaul

3. Problems with Airspeed Safety Switch behind Airspeed Indicator

 

I appreciate any advice or other areas to look at.

[RLCarter]

Sounds like someone used shop air (high PSI) to blow through the pitot tube trashing the airspeed indicator 

[ArtVandelay]

The GUL is connected to both down and up limit limit switches, these are accessed under the belly. My guess bad switch or bad connection... I’d bet on later.

[kortopates]

3 minutes ago, teejayevans said:

The GUL is connected to both down and up limit limit switches, these are accessed under the belly. My guess bad switch or bad connection... I’d bet on later.

I'd check the bulb first. Gear cycling well should eliminate the switches.

[HaldenG]

18 minutes ago, kortopates said:

I'd check the bulb first. Gear cycling well should eliminate the switches.

Bulb tests good.

[ArtVandelay]

I'd check the bulb first. Gear cycling well should eliminate the switches.

Nope, the limit switches are double pole double throw (basically 2 switches tied to same button), so 1/2 of the switch could fail, causing the annunciator problem but the gear still operational. Lucky for the OP.
Not likely, but definitely possible, that’s why I said it’s likely the wiring.
OP: you could try electronic cleaner to see if that fixes the problem. This is a common fix for flap limit switches, but for gear switches I would only use it as a diagnostic tool, and would replace the switches. One of them is very expensive ($350+ IIRC).

[N231BN]

It's easy for someone to trash your airspeed indicator if they don't watch what they're doing on a pilot-static test. Also, these instruments don't last forever and I'm guessing yours is 30+ years old.

They(Century) were unable to rebuild mine so I had to buy one outright.

[HaldenG]

Turned out the airspeed indicator was old and had some internal problems.  With a new airspeed indicator everything is working as it should.

[lifendet]

Im guessing your gear retraction problem was tied into the airspeed indicator?

[HaldenG]

I'm guessing so.  All they did was replace the airspeed indicator and my gear unsafe light is functioning properly now.