Fastest 170 in the fleet!

[jaime72]

I figure I best bring my airspeed indicator woes to the Hanger forum! I am guessing I may have one of the fastest 170's out there, yet the saga continues.

When I arrived to the tie-down to troubleshoot this morning my plane was indicating about 50 - 70 kts! How fast do you fly tied down? After throwing the ceramic heater into the cabin to warm things up I only got faster and faster! By the time preflight was done I was indicating 120kts! That was with the mixture full lean and the ignition off. Imagine those fuel flow rates for 120kts! The places you could go (if you weren't tied down!)

Unfortunately I didn't even get into the air (another story all together) to test things out. But I did get the stall warning indicator to work intermittently (hammer did the job). I will probably pull the ASI tomorrow and drop off at Merrill Field Instruments for a test. A rather new indicator if I remember. When I returned to the airport late this afternoon (after warmer (below freezing still)) temps and some sun I was indicating 0 kts once again.

Stay tuned.

Jaime

[GAHorn]

When it begins to make fuel...don't say a WORD about it. Just drain the excess, donate it to charity, deduct the taxes AND the fuel donations,... and share the tax write-off with ME!

[Bruce Fenstermacher]

Jaime,

Does your plane have any Red or Green in the paint scheme?

Your problem is most likely ice in your pitot line and not the instrument itself. Chances are the blockage is in the first foot of the pitot out at the wing. You need to get the plane in a heated hanger or heat the wing and pitot tube with a preheater to melt the ice and blow out the pitot system before you spend money on the ASI

Next time you see airspeed indicated while standing still get under the panel and disconnect the ASI and it will drop. If not THEN it is in the ASI

I know because I HAVE THE FASTEST 170 having indicated over 180 in level flight with reduced power.
(and being my plane is maroon, a close shade to red, it only stands to reason right George? )

On one of these fast flights the ASI actually went full scale and started over again. I thought, dam know I'm going to have to get the ASI fixed as well as blow out the pitot. Well maybe I was lucky but after clearing the pitot the ASI worked as well as it had before. (Notice I didn't say it worked perfect but only as well as it had. )

(FYI Jaime you will only appreciate the reference to aircraft color with regards to speed after reading ALL the old posts from the last 10 years. Suffice it to say that one area Gahorn might need to study a bit more is color and it's relation to speed regarding to aircraft. )

[jaime72]

White and Burgandy, is that a fast color?

I actually dropped the ASI off to be bench tested. I flew today and it indicated about as well as it always indicated, which was never dead on as I could tell. Towards the end of my flight the airspeed just dropped off to 0 quite suddenly. I was going to blow the pitot from the panel out with a compressor, which obviously means disconnecting the ASI. I decided to just drop the ASI off for a test and pick it up in the morning.

Of course when I dropped it off the guy chuckled. The ASI was serial number 110 of a company out of business. When the closed their serial numbers were about 110 and three more zero's. She's old, but been reglassed and faced. Probably wouldn't be repairable.

So, if I do have to buy a new ASI, suggestions? I prefer dual scale, and if not dual scale I would go to knots. BTW Bruce, you were 180 with the power back, I was 180 with the tie-down's and wing covers still on the plane !

Jaime

[johneeb]

................. BTW Bruce, you were 180 with the power back, I was 180 with the tie-down's and wing covers still on the plane !
Jaime

Jamie if you are going to fly her with the tie-downs and Wing covers still on you had better fly at least 180!

[blueldr]

I had a terrible time trying to improve the accuracy of the asi when I first got my airplane. That was a long time ago, and I don't rightly remember just what the problem was. I do remember that I finally noticed that the altimeter and R/C began moving before I left the ground on take off. When I vented the static system to the cabin, everything worked as intended. As a result I decided to install another static port on the opposite side of the boot cowl and tee them together. That didn't work either. After a good many different combinations tried, I finally jost vented the static system to the cockpit and it's been that way ever since. It seems to be very accurate now. I've compared instrument readings with a number of friends when in flight flying together and both the altimeter and air speed seem to be right on.

[jaime72]

Allright smart people. Step forward and take a chance to earn fame, fortune and the respect of your peers!

My ASI saga continues, $585 DOLLARS LATER! That's right. Merrill Field Instruments tested the ASI and said the problem was a leaky static port. Didn't make too much sense, but they ARE the experts. So a new United indicator was purchased, painted, and installed today.

Test Flight #1:

Pitot cover lifts up on taxi. No indication of airspeed on takeoff. Normal takeoff. During climb-out at approximately 300' indication slowly starts to increase. ASI indicates higher at higher angles of attack regardless of groundspeed during calm wind conditions. Indicates erratically for short period of time (10 minutes?) prior to indicating 0mph for remainder of flight.

Could be me, but I thought the VSI indicated a decent even during a climb for the first 10 minutes of flight.

Altimeter read 300' difference from GPS Altitude though indicated field elevation with current altimeter setting.

Thoughts? Idea's?

Thanks in advance,

Jaime

[hilltop170]

Did you blow out the lines while in above freezing conditions? Could still have a blockage somewhere?

[GAHorn]

Allright smart people. Step forward and take a chance to earn fame, fortune and the respect of your peers!

My ASI saga continues, $585 DOLLARS LATER! That's right. Merrill Field Instruments tested the ASI and said the problem was a leaky static port. Didn't make too much sense, but they ARE the experts. So a new United indicator was purchased, painted, and installed today.

Test Flight #1:

Pitot cover lifts up on taxi. No indication of airspeed on takeoff. Normal takeoff. During climb-out at approximately 300' indication slowly starts to increase. ASI indicates higher at higher angles of attack regardless of groundspeed during calm wind conditions. Indicates erratically for short period of time (10 minutes?) prior to indicating 0mph for remainder of flight.

Could be me, but I thought the VSI indicated a decent even during a climb for the first 10 minutes of flight.

Altimeter read 300' difference from GPS Altitude though indicated field elevation with current altimeter setting.

Thoughts? Idea's?

Thanks in advance,

Jaime

Jaime, I merged these two posts since they are really/truly the same continuing discussion. (It's best to keep the subject together when you follow up on previous topcs, so that ALL the previous discussion is available to inform new visitors t o the topic.)

Did Merrill look only at your indicator on the bench? Or did you allow them to perform a pitot-static system test of you airplane? (That's what I'd do...I'd let 'em have the entire plane and sort it out.)

[jaime72]

They bench tested the unit. Next step is the pitot/static system. I just couldn't think of anything that would cause those types of airspeed indications and not affect the VSI and altimeter.

Thanks for the merge.

Jaime

[jrenwick]

....Pitot cover lifts up on taxi. No indication of airspeed on takeoff. Normal takeoff. During climb-out at approximately 300' indication slowly starts to increase. ASI indicates higher at higher angles of attack regardless of groundspeed during calm wind conditions. Indicates erratically for short period of time (10 minutes?) prior to indicating 0mph for remainder of flight.

The "altimeter mode" ASI, where indicated airspeed follows altitude, is the textbook symptom of a plugged pitot tube or line. In combination with that, the sensitivity to AoA would be due to variations in the static pressure line caused by a leak. If the indicated airspeed increases during a climb and then goes to zero in level flight, then there's a leak in the pitot line as well, or the blockage isn't quite complete.

My 170's VSI always indicated a 100FPM descent in level flight until I had some avionics work done and the mechanic restored its connection to the static line. (It looked like it had been disconnected when the encoder was installed -- somebody just borrowed the VSI's static connection and hooked it up to the encoder, leaving the VSI "connected" to cabin pressure.)

It sounds to me like you may have a combination of a blocked pitot tube or line and a static system leak, and maybe a leak in the pitot line as well. Do what George said, though. Let the shop have the whole airplane, because they have test equipment that will let them really sort it all out. It's so nice to have everything working right!

[jaime72]

Wowa! Sorry, I forgot to post the update.

So the new ASI didn't fix the problem. Shucks! $585 for almost nothing. Though the old ASI did have the static leak, was old, and wasn't the best for the 170's airspeed range. We replaced it with a new United 20-160mph ASI. Pretty slick with the custom paint job and Vx, Vy and Va marks. So at rotation the ASI needle is at about 3 o'clock as opposed to 1:30 o'clock.

She spent the night in the Merrill Field Instruments hanger a couple weeks ago. Two nights actually, they were quiet. It coincided with wind, wet snow and a re-freeze. Perfect timing!

The guy at MFI would blow the pitot out every couple hours throughout the day between other jobs.

VOILA! She has worked flawlessly since. He mentioned a small amount of water blowing out the line, but nothing significant. Obviously enough to give me a headache. Everything else checked out good. I have flown about 45 hours this past month learning the plane and working things out. Couldn't be happier.

Thanks again for the input.

Cheers,

Jaime Andersen
1954 Cessna 170B
N2886C, Serial #26429

[cessna170bdriver]

...VOILA! She has worked flawlessly since. He mentioned a small amount of water blowing out the line, but nothing significant. Obviously enough to give me a headache. Everything else checked out good. I have flown about 45 hours this past month learning the plane and working things out. Couldn't be happier.

Proof that a small amount of water IS significant when it comes to pitot lines. Glad you got your problem solved!

Miles

[blueldr]

When I was having the water problem in my pitot line, it was slowly migrating down the pitot line until it settled in a low spot in the line behind the upholstery located between the front door post and the instrument panel. This then choked the line off. It was a pain to get to and back blow the line so I put a tee in the line at that point and ran it down into a small plastic bottle which I emptied on the annual. After I installed a pitot head beneath the wing, the problem disappeared.

[Azpilot]

Jaime,


I know because I HAVE THE FASTEST 170 having indicated over 180 in level flight with reduced power.
(and being my plane is maroon, a close shade to red, it only stands to reason right George? )

)

Thats pretty good.

The fastest I've gotten mine was 160kts true at 20,000 with the turbo on and sucking oxygen.