Tach goes haywire during climb out

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deaston

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Dan
This is probably no big deal to the veterans, but as a student pilot it certainly got my attention.

I was just climbing out for my first big solo XC. About 400' AGL I looked down and noticed the tach needle bouncing all over the place, along with an odd whine that seemed in sync with the needle bouncing. The engine seemed to be producing smooth power but it definitely gave me an Oh, $&/! Moment. I contunued to climb to pattern altitude and turn on course as I deliberated on how to handle. I was pretty sure the engine was fine, based on the performance, smoothness, and otherwise "normal-ness" of everything but the tach needle. I also noticed that as I reduced power, the needle settled down a good bit. I did consider continuing (the thought of do I really need the tach? Crossed my mind), but after what in hindsight seems WAY to long (I probably got a mile out), I decided to call tower to come back and land. Fortunately we have a quiet airport and there was zero traffic.

Turned out to be a harmless tach problem, which has been replaced. On one hand, I'm proud of myself for not completely freaking out and doing something really stupid. On the others hand, I think I really should have reacted quicker, stayed in the pattern, and landed immediately.

If it had been an actual emergency, it really has me questioning whether or not I would have made the quick decisions necessary... Also has me paying much closer attention to what lies beyond the end of the runway. Hopefully I'll never have to find out up close and personal.

Just thought I'd share. Hoping tomorrow will be the day to get the XC done!
 
deaston said:
If it had been an actual emergency, it really has me questioning whether or not I would have made the quick decisions necessary... Also has me paying much closer attention to what lies beyond the end of the runway. Hopefully I'll never have to find out up close and personal.
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First off... Welcome to PoA!

Secondly I think because of this you learned a great lesson (and you did handle it very well) so that if there is a next time you will be able to handle it even better!

Goodluck!
 
Welcome To POA.

You handled it well. It was not an emergency as you had good power and no vibration. Hearing the squeal in sequence with the jumping was the clue. A precautionary landing to fix was what wrong was a good call.

All ways remember to fly the airplane first. :yes:
 
Engine was running fine? You were fine.

Had the engine been doing weird things than yeah you wouldve needed to react sooner. The big thing you need to decide is: will the plane continue to fly? In your case yes you were fine no big deal. Ive had an ASI go funky on me. It was just water in the pitot lines. Plane still flew no big problem.
 
Reminds me a bit of one November day when we were flying along in the clouds at 7000 with Fran up front flying, our son in the right seat, and me in the back working on my laptop. All of a sudden Fran hollers "OH [POOP]!" This gets my attention. "The airspeed went to zero!" she continues. "Are we still flying?" I asked. "Oh," she says, "Pitot heat ON...that fixed it. Approach, 64U request immediate descent to 5000 due to icing at 7." I go back to the report I was writing.
 
Tach problems will be with us always. If you get a chance, talk to the shop, ask them to show you the components and normal failure modes. Postponing a student trip is an inconvenience, but postponing a trip you need to make could be costly.

deaston said:
This is probably no big deal to the veterans, but as a student pilot it certainly got my attention.

I was just climbing out for my first big solo XC. About 400' AGL I looked down and noticed the tach needle bouncing all over the place, along with an odd whine that seemed in sync with the needle bouncing. The engine seemed to be producing smooth power but it definitely gave me an Oh, $&/! Moment. I contunued to climb to pattern altitude and turn on course as I deliberated on how to handle. I was pretty sure the engine was fine, based on the performance, smoothness, and otherwise "normal-ness" of everything but the tach needle. I also noticed that as I reduced power, the needle settled down a good bit. I did consider continuing (the thought of do I really need the tach? Crossed my mind), but after what in hindsight seems WAY to long (I probably got a mile out), I decided to call tower to come back and land. Fortunately we have a quiet airport and there was zero traffic.

Turned out to be a harmless tach problem, which has been replaced. On one hand, I'm proud of myself for not completely freaking out and doing something really stupid. On the others hand, I think I really should have reacted quicker, stayed in the pattern, and landed immediately.

If it had been an actual emergency, it really has me questioning whether or not I would have made the quick decisions necessary... Also has me paying much closer attention to what lies beyond the end of the runway. Hopefully I'll never have to find out up close and personal.

Just thought I'd share. Hoping tomorrow will be the day to get the XC done!
Click to expand...
 
Do you have a tach gen and an electric tach guage? the whine suggest that you do...probably the tach gen needed an OH..it happens
 
deaston said:
This is probably no big deal to the veterans, but as a student pilot it certainly got my attention.

I was just climbing out for my first big solo XC. About 400' AGL I looked down and noticed the tach needle bouncing all over the place, along with an odd whine that seemed in sync with the needle bouncing. The engine seemed to be producing smooth power but it definitely gave me an Oh, $&/! Moment. I contunued to climb to pattern altitude and turn on course as I deliberated on how to handle. I was pretty sure the engine was fine, based on the performance, smoothness, and otherwise "normal-ness" of everything but the tach needle. I also noticed that as I reduced power, the needle settled down a good bit. I did consider continuing (the thought of do I really need the tach? Crossed my mind), but after what in hindsight seems WAY to long (I probably got a mile out), I decided to call tower to come back and land. Fortunately we have a quiet airport and there was zero traffic.

Turned out to be a harmless tach problem, which has been replaced. On one hand, I'm proud of myself for not completely freaking out and doing something really stupid. On the others hand, I think I really should have reacted quicker, stayed in the pattern, and landed immediately.

If it had been an actual emergency, it really has me questioning whether or not I would have made the quick decisions necessary... Also has me paying much closer attention to what lies beyond the end of the runway. Hopefully I'll never have to find out up close and personal.

Just thought I'd share. Hoping tomorrow will be the day to get the XC done!
Click to expand...

Tach drive cable needs grease, heads go bad... if the engine sound doesn't change, just ignore things like that in flight and report it to maintenance when you get back. S-t happens, just fly the plane.;)
 
Henning said:
Tach drive cable needs grease, heads go bad... if the engine sound doesn't change, just ignore things like that in flight and report it to maintenance when you get back.
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I just had a new tach cable installed as well. Mine is jumping as well. What kind of grease are they supposed to use?
 
Marauder said:
I just had a new tach cable installed as well. Mine is jumping as well. What kind of grease are they supposed to use?
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I always use Lubriplate White Lithium Grease, but there are others that are just fine. You want one that isn't too cold sensitive. You may also want to look for tight bends. Also if the magnets get some scrud between them.
 
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Thanks for the warm welcome.

After landing, I talked to my instructor. He thought it was a bad cable as well, but ended up replacing the tach itself. I haven't had a chance to find out more, but looking good for tomorrow.
 
These things have tach CABLES? It's a wonder we can use them for anything. The usual way to drive a tach is electrically, using the ignition system (perhaps inductively). Tach problems in other contexts often point to ignition problems.
 
MAKG1 said:
These things have tach CABLES? It's a wonder we can use them for anything. The usual way to drive a tach is electrically, using the ignition system (perhaps inductively).
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That may true in cars, but it is not true in light planes, especially light singles other than those with glass panels or those which have been modified by the owners (like my Tiger with its JPI EDM-930). Mechanical tachs remain the norm.
 
MAKG1 said:
These things have tach CABLES? It's a wonder we can use them for anything. The usual way to drive a tach is electrically, using the ignition system (perhaps inductively). Tach problems in other contexts often point to ignition problems.
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And the reason they still have tach cables is the same reason that we still use 30's technology on certified airplanes. For the manufacturer to make even small changes like an electronic tach costs thousands of dollars and a blizzard of paperwork. Homebuilders have been using highly accurate electronic gauges for almost 20 years. Another reason certified airplanes cost an insane amount of money. Don
 
Well, I think the first car with an electornic tach I had was my 1980's-ish Datsun. The Fiat 128 I drove before that had a mechanical one. Most aircraft date from the mechanical tach era and there hasn't been a compelling reason to change.

There are non-glass panel aircraft with electronic tachs, but they're typically newer ones. My engine instruments are all out of an A36, and unlike my old 1950's gauges in the Navion there are no cables, oil capillary lines, or temperature probes sticking through the firewall anymore.
 
MAKG1 said:
These things have tach CABLES? It's a wonder we can use them for anything. The usual way to drive a tach is electrically, using the ignition system (perhaps inductively). Tach problems in other contexts often point to ignition problems.
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About 50/50 in GA planes between cable and electric drives. Nothing wrong with cables an the advantage is when you have a problem any speedometer shop can build you a new core for a few $ and adjust the magnets if it gets out of calibration.
 
flyingron said:
Well, I think the first car with an electornic tach I had was my 1980's-ish Datsun. The Fiat 128 I drove before that had a mechanical one. Most aircraft date from the mechanical tach era and there hasn't been a compelling reason to change.

There are non-glass panel aircraft with electronic tachs, but they're typically newer ones. My engine instruments are all out of an A36, and unlike my old 1950's gauges in the Navion there are no cables, oil capillary lines, or temperature probes sticking through the firewall anymore.
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Electric (not electronic, just simple generator with a voltmeter calibrated in RPM) have been around since before WWII.
 
MAKG1 said:
These things have tach CABLES? It's a wonder we can use them for anything. The usual way to drive a tach is electrically, using the ignition system (perhaps inductively). Tach problems in other contexts often point to ignition problems.
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Yup.
When my tach went wonky, an electronic tach went in. Problems solved.
 
PilotAlan said:
Yup.
When my tach went wonky, an electronic tach went in. Problems solved.
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Yep, mine died in actual with a CFI, freaked center out when we told them we had an engine instrumentation issue.:lol:

I just left the blue knob alone till I had runway in site.

Now have an EI, cable comes out this annual.
 
Skylane81E said:
Yep, mine died in actual with a CFI, freaked center out when we told them we had an engine instrumentation issue.:lol:

I just left the blue knob alone till I had runway in site.

Now have an EI, cable comes out this annual.
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Nice thing with a twin, you lose one tach, you just keep them in synch by ear and run off the other. It's not like electric & electronic tachs don't have wire issues...;)
 
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