Even in God’s country, it rains and can be ugly. Today is such a day so I thought I would take a moment and reflect on a couple of things that I thought might be of interest to SRXX owners.
Intercom/music in flight - not long ago there were some posting about CD and MP3 players, but we did not talk about something that 'bugged me early on Â…. intercom ‘traffic’ interrupts the music! My bride, who is a quite gifted singer (I had to say that), likes to sing along and when she does it stops the music. She was frustrated. Actually so was I when I “sang” when flying along Â… the only way I would dare “sing”. The solution is in the Garmin audio unit. The Garmin 340 can be setup to NOT mute the music input when there is intercom traffic. I initially asked Cirrus to set mine 340 up so that the intercom would not mute the music, but was told they would not do that. Instead of ‘hardwiring’ the change, the avionics shop installed a switch, which I had mounted next to the flap switch, that allows me to choose whether or not to allow intercom traffic muting. It works like a champ.
Hobbs time - The current setup on all Cirrus aircraft is to use a hobbs meter to keep track of time. I found this to be very frustrating and down right maddening. What brought this to light was Paul T’s trip to Napa this last weekend. He was held on the ground pending IFR release for over 30 minutes (the SFO does have some problems). Using the Hobbs meter he racked up 30 minutes of ‘flight time’ that did NOT happen. It becomes even more maddening when you attempt to use your hobbs time to calculate overall aircraft performance. Simply things that fuel burn or oil consumption is hampered by absence of a recording tach. I know that some people have installed an airswitch and I have installed a manual switch that I turn on and off when I takeoff and land. I know have very good record of flight time NOT alternator time.
There are problems with either the airswitch or the manual switch. Until Garmin or someone else provides a “feed” from either the new 327 (transponder flight timer) or the GNS 430 to activate a timer such as the hobbs, you have to cut into the pitot line to make it work. It is the cutting into the pitot/static system that makes me nervous and would require some paperwork. Using a manual switch has some problems, but are much simpler problems Â… remembering to turn it on and off at the appropriate times. There is also the possibility that a future buyer might think that the owner was trying to hide some hours, which I am not, but there is always the suspicion.
PS - the sixth vacuum pump is doing fine and now has over 50 hours on it Â… knock on wood.
Is there a tachometer that records only “air time” by using only rpm’s above a certain level?
Hobbs time - The current setup on all Cirrus aircraft is to use a hobbs meter to keep track of time. I found this to be very frustrating and down right maddening. What brought this to light was Paul T’s trip to Napa this last weekend. He was held on the ground pending IFR release for over 30 minutes (the SFO does have some problems). Using the Hobbs meter he racked up 30 minutes of ‘flight time’ that did NOT happen. It becomes even more maddening when you attempt to use your hobbs time to calculate overall aircraft performance. Simply things that fuel burn or oil consumption is hampered by absence of a recording tach. I know that some people have installed an airswitch and I have installed a manual switch that I turn on and off when I takeoff and land. I know have very good record of flight time NOT alternator time.
I thought I’d answer my own question after looking in an Aircraft Spruce catalog. Electronics Intl. makes an electronic digital/analog tach that records time the engine operates above 1300 rpm, as well as an automatic flight timer that operates only when above 2,000 rpms. The cost is $405. Accuracy is within 1%. I assume Cirrus has a mechanical one where the accuracy is usually off at least 30 rpm at best, and idling and taxing is probably recorded. TS Culhane makes another one, according to a post I saw on the AOPA “Mechanics Bench” forum, available at Gulf Coast Aviation. It would seem wise to install one of these on a new plane, if possible, to more realistically indicate your flight time. You’d also save maintenance costs (time between oil changes, for ex.) and your aircraft would be a little bit slower on the road to TBO. Plus, accuracy would be better.
Is there a tachometer that records only “air time” by using only rpm’s above a certain level? I’d be interested in some thoughts on this.
Is there a tachometer that records only “air time” by using only rpm’s above a certain level?
Recording Tachs generally record an hour for an hour at cruise RPM. At idle time is still recorded but at a much slower pace. However, all the owner needs to do is keep track of flight time; ie, from the time the plane leaves the earth to the time in returns. As to your question I am not aware of any tach that records only air time.
Gary - that’s great to know. I think I will have to look into that. BTW, the Cirrus Tach is electronic.
I assume Cirrus has a mechanical one where the accuracy is usually off at least 30 rpm at best, and idling and taxing is probably recorded.
The SR20 does not have a recording tach! The only time recorder is the Hobbs meter, which is wired to the alternator, so essentially while the engine is turning, the meter is counting, and counting clock time, not engine RPM equivalent time.
We installed an airswitch in our SR20, and fitted a second (electronic) hourmeter. It starts counting at a preset airspeed (set to be just below stall speed). Whenever I fly, the airswitch recorded time is always 0.2 hours less than the Hobbs time per takeoff and landing.
It was fitted by a LAME (Oz equivalent of an A&P) and while I don’t know the exact cost, it was way less than the US$405 that a new recording tach would evidently cost (I recall being told beforehand it would be about $200).
It does connect into the pitot line, but if it is done by a qualified mechanic, this should not be a problem.
Maintenance etc. is all calculated on the airswitch time. Personally, I can’t think of any good reason not to simply connect the airswitch to the existing Hobbs meter, but we ended up with two.
I have one of the EI units in my C-172 and I will put it in any plane I own in the future. Of course the accuracy is terrific but I can’t say enough about the digital display. Maybe I’m overally…what’s a good word here ;)… but dialing in and looking at digits, particularly during the run-up is important.
Second, it does not record time until 1,700 rpm and as mentioned elsewhere this saves time and money in maint.
At the time they only had the small diameter gauge, I would opt for a larger one next time, but only for looks. I have no trouble reading it, the LCD’s are backlit and adjust with the panel lighting. The LED’s that form the ‘Analog’ portion adjust inversley with the panel lighting.
I thought I’d answer my own question after looking in an Aircraft Spruce catalog. Electronics Intl. makes an electronic digital/analog tach that records time the engine operates above 1300 rpm, as well as an automatic flight timer that operates only when above 2,000 rpms. The cost is $405. Accuracy is within 1%. I assume Cirrus has a mechanical one where the accuracy is usually off at least 30 rpm at best, and idling and taxing is probably recorded. TS Culhane makes another one, according to a post I saw on the AOPA “Mechanics Bench” forum, available at Gulf Coast Aviation. It would seem wise to install one of these on a new plane, if possible, to more realistically indicate your flight time. You’d also save maintenance costs (time between oil changes, for ex.) and your aircraft would be a little bit slower on the road to TBO. Plus, accuracy would be better.
Is there a tachometer that records only “air time” by using only rpm’s above a certain level? I’d be interested in some thoughts on this.
Gary - that’s great to know. I think I will have to look into that. BTW, the Cirrus Tach is electronic.
Gary - that’s great to know. I think I will have to look into that. BTW, the Cirrus Tach is electronic.
Please let us know what you find out. Perhaps, it’s not so easy just to change one out. But, IMHO, I don’t see how you cannot do something about this problem (and you did deal with it in another way). No one wants to run up time on the engine and airframe that doesn’t really exist.
Is there any reason to NOT COUNT all engine revs?
Wouldn’t that amount to “kidding one’s self”?
An ostrich ignores conflict by burying its head in the sand, but then ostriches don’t fly.
TACH Time does not equate to Airborne Time, expressed as leaving the earth and returning. It simply counts cumulative engine revs. Engine revs data provide means to anticipate maintenance events.
MFG’s recommended TBO=2000Hrs = 120,000Minutes.
The 2000Hrs is only a MFG’s estimate, subject to all manner of operating & service conditions. This TBO translates to something between 120 and 300 million engine revs.
Those 2000Hrs if operating at 100% taxi speeds, 1000rpm, would generate 120,000,000 engine revs; while if operated at 100% cruise, 2500rpm would be 300,000,000 engine revs.
Whether spent in taxi, hold short, or cruise, we are still “spending” the available engine revs.
Is there any reason to NOT COUNT all engine revs?
Yes, several. Firstly, maintenance of the entire airframe is supposed to be based on flight hours, which is not accurately measured by engine revs.
Secondly, one revolution of the crankshaft at idle will cause a lot less wear on the engine than one rev at full or cruise power - the sresses on the bearings, rings etc. are way lower.
Thirdly, the manufacturer’s published TBO is based on “time in service” which is defined as flight time - wheels off to wheels on. It’s in the FARs.
Finally, there are many factors that contribute to engine wear and therefore lifetime - the manufacturer’s quoted TBO is at best a educated guess. In private use, I believe there is nothing to stop you maintaining your engine “on condition”. I have an interest in an aircraft with a Lycoming O-360 that ran perfectly till 2200 hours, at which time it was decided to overhaul it not because it showed any signs of needing it, but because of the paperwork needed to continue flying it (in non-private use) past TBO.
If you look after your engine, it is not going to suddenly quit when it reaches published TBO (some engine types have a reputation for not making it that far) and no method of counting hours is going to tell you when it needs work. The engine will tell you that.