In the last two weeks I installed my new C/S Hartzell Prop AD free. Smooth On the first flight the tach read the same on take off rpm as the old prop. Now I installed a Horizon elect tach and found I have been flying with a max rpm of 2564 LYC O360 red line is 2700 rpm. So I'll bump it up to about 2675. I found I adjusted pretty quickly to the digital read out, but I have run alot of different aircaft types and test cells and can sink the throttle movement to the digital movement and stop at a number that I'm trying to hit. I tend to choose the last digit as 5 so only it moves up and down one or two digits and doesn't move the last two digits. Less distracting Lance
Weight & balance, my old Grimes beacon was frozen again last week may have to address that now, test runup, and then I should be ready for the first flight. Weather may be a factor though, it's snowing now.
Does the Horizon tach have a feture that allows you to set the increments at 5 rpm vs. 1 rpm? If I read your post correctly, the engine RPM might change 3-4 RPM but the only time you see a change is when you change at least 5 RPM ??
Sounds like a cool way to avaid chasing RPM when setting the throttle - of course the fixed pitch will vary differently then the C/S anyway.
Kyle-
From past experience with these tachs, Horizon is very rigid about making any changes at all so I would say they won't change the last digit to 5rpm increments.
For instance, the annunciator lights on top go green, yellow, red from left to right. Just below them is a placard with the actual rpm limits spelled out. The order on the placard is red, yellow, green. Doesn't make sense to me but they won't reverse the order because it was certified that way.
Then there's the actual value of RPM limits. The C-170 book says; green, 2200-2450; yellow, 2450-2700; red, 2700. Horizon says; green, 2200-2449; yellow, 2450-2699; red, 2700. Still doesn't make sense and is confusing but they still won't change it because, you guessed it, that's the way they certified it.
It doesn't matter how Cessna certified it or what common sense tells you, that's the way it is. I have spent several calls with them hoping to get a different guy to discuss it with who might be sympathetic but they all hold the party line to the last man, er tech rep.
Other than that the tachs themselves are wonderful pieces of equipment, I would never go back. It takes no time at all to get used to them. The last digit is insignificant.
I got mine approved on a 337 w/reference to installation iaw STC SA5820NM except installed on a C-170A instead of a C-172. My engine is an O-300-D, from a C-172.
EI also makes a good electronic tach that works just as well and is 2-1/4" instead of 3-1/8" if you need some more space in the panel.
Last edited by hilltop170 on Thu Jan 25, 2007 2:05 am, edited 2 times in total.
Richard Pulley
2014-2016 TIC170A Past President
1951 170A, N1715D, s/n 20158, O-300D
2023 Best Original 170A at Sault Ste. Marie
Owned from 1973 to 1984.
Bought again in 2006 after 22 years.
It's not for sale!
I just ran into a problem with this Tach. It is NOT certified for the Cessna, in fact if I'm understanding my mechanic it's not certified at all! They advertise it as being STC'd for primary instrument replacement, but the paperwork is still pending at the FAA.
Horizon is sending us a 337 copy to hopefully get the situation resolved, but if that doesn't get approved?!?!?!! It looks like a good unit, but I feel like I've been taken for a $600 ride, and I wont be happy till I either get my money back or the thing is mounted and working as advertised.
Well - thats an interesting take on it. I'm suprised that they don't adjust the tach to meet the aircraft / engine peramiters. By doing so one would anticipate it's approval in more aircraft ..
This tach is STC'd for many aircraft. You happen to be putting it on a Cessna 170 which it is STC'd for, with a LYC O-360 configuration which they don't have a STC for but they have the paper work in at the FAA to get it added to their list. Since it is an engine instrument with the engine limits on the gauge and your putting it a Cessna 170 The STC has to be approved for that configuration. Not a big deal for them. I had them send it ahead so I could get it installed and expect the approval STC in short order. Meanwhile I'm changing the encoder. Putting in a Garmin transponder and going from a Loran to a Garmin GPS. Now the digital tach runs up and down the scale or range normally. Stopping it at increments ending in five allows for the small movment of rpm from forces more powerful than us. Not to make the second digit move, breaking my consintration which is the only thing holding the plane up in the air. There by sending me herdeling toward the earth. Lance
I wasn't going to say anything when I saw this thread. Last year I ordered one from Spruce but before it got to me they said that although it was STC'd for certain Cessna models it wasn't STC'd for a Lycoming powered 170. I declined to accept it. You can wait for the STC but thats a familiar promise. You could be waiting like the guys with the Avion panel, oh I'd say its been about at least 8 years now but its coming.
Just a follow up on the Horizon elec tach. I have from time to time had another aircraft type added on to a manufacturers STC. From batteries to oil filters. This Horizon tach is installed new on some production aircraft and has a TSO approval. Their STC has a varied number of aircraft types and they are actively adding to it. That’s a far cry to a panel that never had an STC and has no support from the manufacturer or the FAA. Field approvals come in where the number of possible installations on a specific type doesn’t warrant the manufactures time and effort to obtain the addition of that aircrafts type certificate to his STC. Using their STC as a basis for approval in the FAA's narrowed categories of what they will even consider allowing field approvals for. The hold up is on the FAA’s side and probably due to manpower. They are retiring and the FAA are not keeping up with the changes in aviation or technology. From talking to Horizon they seem to have an on going approval process in place and I have no fears of it not being approved in the near future. Lance RNO
Watkinsnv wrote:Just a follow up on the Horizon elec tach. I have from time to time had another aircraft type added on to a manufacturers STC. From batteries to oil filters. This Horizon tach is installed new on some production aircraft and has a TSO approval. Their STC has a varied number of aircraft types and they are actively adding to it. That’s a far cry to a panel that never had an STC and has no support from the manufacturer or the FAA. Field approvals come in where the number of possible installations on a specific type doesn’t warrant the manufactures time and effort to obtain the addition of that aircrafts type certificate to his STC. Using their STC as a basis for approval in the FAA's narrowed categories of what they will even consider allowing field approvals for. The hold up is on the FAA’s side and probably due to manpower. They are retiring and the FAA are not keeping up with the changes in aviation or technology. From talking to Horizon they seem to have an on going approval process in place and I have no fears of it not being approved in the near future. Lance RNO
I'm not sure I understand what you mean about using their STC as a basis of approval, Lance. Do you mean as a basis of approval for a field approval?
I believe it's contrary to policy for the FAA to issue a field approval based on an STC. An STC is proprietary and ...if one exists for a product...then the FAA is to disallow any field approvals based upon that proprietary data. The STC holder must make application otherwise. (That's what I've been told by some impressively credentialed FAA types. Perhaps some inspectors are just not fully in compliance, tho'.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention. An originality nut (mostly) for the right reasons.
That far cry is closer to the issue than I had though of; Avion does have STC's for some of their panels. I could be wrong but I think they had one for a 172A model, a panel thats almost identical to latter model 170 panel. Should have been a no-brainer. Whether there's a positive individual at the controls or not still doesn't give you the piece of paper to make it work. I think what George has been trying to say for sometime is, first the paper then the parts. I think its was two years ago, maybe three when I almost had to pay for the Horizon from Spruce. Hey it could happen tomorrow but the process for approval as you have pointed out is a factor of the number of units sold times the amount of time and effort to get an STC for a specific application.
That's a good analogy, Jim.
The Avion instrument panel is a story I've gotten several times from various members. It's understandable from the perspective of an STC holder, but not appreciated by some 170 owners of that panel.
In a few cases I know of , a person buys an airplane in which the panel is not fully/properly documented. In a subsequent annual inspection the inspector questions the installation basis of approval.
Of course, the FAA won't field approve it for several reasons. (An STC holder is involved. Addt'l modifications to the aircraft other than simple panel mod is involved, including ....big warning flag.... primary flight control changes. And there's no engineering data to support the major alterations necessary to install that panel, therefore there's no way to tell if THIS installation is identical to ANY APPROVED installation. It LOOKS similar, but there's danged few written descriptions of the actual work performed and there's NO engineering data, drawings, specs, etc etc.)
The new owner of the airplane doesn't understand why Avion won't supply that info without some money. It's not apparent that Avion 1)-has no idea of the actual modifications that took place when their panel was installed, if it was altered, if the flight controls are airworthy, etc etc., and 2)- has little interest in assuming liability for an installaiton that has not paid them for engineering work.
From Avion's perspective, they sold a penel only, and the original purchaser bought it knowing they were not paying for any STC or other approvals. They understandably have little interest in solving a subsequent purchaser's problems without being paid for additional work performed.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention. An originality nut (mostly) for the right reasons.
Yes, your right. I mean with the approval of the owner of the STC or in the case of the Aero Flash Signal Strobe kit. It is a PMA'd part with 11 Cessnas on the approvel list. When Aero flash sell's it to you for a Cessna 170 and says feel free to get a field approval for it. The FAA is much more likely to approve it, as they did with mine. When I did my Del Air conversion I went well past the STC with field approvals some noting the use on the 172 on his own STC like the 172 nose cowl and oil door I manufactured for it. The engine driven vacuum system that comes with the engine but is not mentioned in the STC. That is added and uses the STC as a basis for the field approval. Also the verner mixture and throttle controls. The STC calls out for a verner prop control. Hay how about for consistancy we put in all three. Presto field approval. Lance
Cessna® is a registered trademark of Textron Aviation, Inc. The International Cessna® 170 Association is an independent owners/operators association dedicated to C170 aircraft and early O-300-powered C172s. We are not affiliated with Cessna® or Textron Aviation, Inc. in any way.
On the first flight the tach read the same on take off rpm as the old prop. Now I installed a Horizon elect tach and found I have been flying with a max rpm of 2564 LYC O360 red line is 2700 rpm. So I'll bump it up to about 2675. I found I adjusted pretty quickly to the digital read out, but I have run alot of different aircaft types and test cells and can sink the throttle movement to the digital movement and stop at a number that I'm trying to hit. I tend to choose the last digit as 5 so only it moves up and down one or two digits and doesn't move the last two digits. Less distracting 
Lance
