Private Hire: VDO vs Airswitch
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Private Hire: VDO vs Airswitch
I dropped in to the local aeroclub the other day to enquire about private hire rates and was somewhat disapointed to see on the bottom of the page with all the details,
"NB. All charges are start-up to shutdown - clock or VDO not airswitch."
Its been a fair while since I private hired something but I remember the place that I learnt to fly would charge VDO when it was dual or airswitch/tacho time for private hire.
Now I know we are ALL professional about what we do (right???) but it seems to me it would encourage bad behavior like mag checks on taxi or not waiting till the oil temp was in the green before blasting off etc etc. Hopefully this wouldn't happen but the cynic in me says it must make it more likely?
Is this the generally excepted standard now adays? Anyone out there private hire using airswitch? Is the maintance still calculated on airswitch? That could be a factor I guess.
On a side note the C172 at this regional city goes out at $215.00 for non members. Its a fairly universal aircraft, wondering what others are charging round Oz if you know??
"NB. All charges are start-up to shutdown - clock or VDO not airswitch."
Its been a fair while since I private hired something but I remember the place that I learnt to fly would charge VDO when it was dual or airswitch/tacho time for private hire.
Now I know we are ALL professional about what we do (right???) but it seems to me it would encourage bad behavior like mag checks on taxi or not waiting till the oil temp was in the green before blasting off etc etc. Hopefully this wouldn't happen but the cynic in me says it must make it more likely?
Is this the generally excepted standard now adays? Anyone out there private hire using airswitch? Is the maintance still calculated on airswitch? That could be a factor I guess.
On a side note the C172 at this regional city goes out at $215.00 for non members. Its a fairly universal aircraft, wondering what others are charging round Oz if you know??
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I would agree that it is a load of bs that they charge on startup to shutdown. Your right, i think it probably does lead to people pushing the min time on the ground. I am finding this is the norm to charge the whole time which is dumb, since maintenance time is based on airswitch. Spose not much you can do at the end of the day, its just damn annoying
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Also be aware that you could be charged from the moment you turn the battery on!
Have seen the VDO tick over just while a couple of waypoints were being put into the GPS.... No engine running!
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Have seen the VDO tick over just while a couple of waypoints were being put into the GPS.... No engine running!
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Both methods (air time and engine-running time) have valid and reasonable reasons for being used.
From the flight-schools perspective, they are paying for fuel and (possibly) a captive on-board instructor while the engine is running.
From the owners perspective they pay for maintanence when the aircraft actually flies and the engine is producing significant power.
If the ground time is significant compared to the airtime (eg doing circuits at a place where the parking area is a long way away from the runway) then VDO time is fairer because someone has to pay for the fuel (and instructor if applicable)
But if the ground time is small in comparison to the airtime (eg a 4 hour cross-country) then either method will produce a similar total cost and there's not much $ to be saved by speeding-up runnups. After all, the enroute winds on a long trip will have more influence on the total trip time.
From the flight-schools perspective, they are paying for fuel and (possibly) a captive on-board instructor while the engine is running.
From the owners perspective they pay for maintanence when the aircraft actually flies and the engine is producing significant power.
If the ground time is significant compared to the airtime (eg doing circuits at a place where the parking area is a long way away from the runway) then VDO time is fairer because someone has to pay for the fuel (and instructor if applicable)
But if the ground time is small in comparison to the airtime (eg a 4 hour cross-country) then either method will produce a similar total cost and there's not much $ to be saved by speeding-up runnups. After all, the enroute winds on a long trip will have more influence on the total trip time.
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Hi,
Few years back, I was charged from START UP to SHUT DOWN for a single engine constant speed prop. and at the same place, I was charged Airswitch for a Multi Engine. I called up the bloke at the same place few days ago for a planned private hire next week, and they still do the same.
Point is, if it is a single engine with not too much before take off hassles, and operating out of say, a typical GAAP, its is fair enough to charge form start to shut.
Regards,
SS
Few years back, I was charged from START UP to SHUT DOWN for a single engine constant speed prop. and at the same place, I was charged Airswitch for a Multi Engine. I called up the bloke at the same place few days ago for a planned private hire next week, and they still do the same.
Point is, if it is a single engine with not too much before take off hassles, and operating out of say, a typical GAAP, its is fair enough to charge form start to shut.
Regards,
SS
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In practice, it makes almost no difference to what you're going to pay after the flight. If you're getting charged airswitch time, you can be certain the rate will be higher than for engine time charges.
If I guess J0N0's local aeroclub correctly, the last time I flew there, their engine switches were all linked to oil pressure, and so only count the time when the engine is running. Never seen one like Buzzy's that started ticking when the master switch was turned on, but I can imagine that some dodgy operator might try such a trick.
If I guess J0N0's local aeroclub correctly, the last time I flew there, their engine switches were all linked to oil pressure, and so only count the time when the engine is running. Never seen one like Buzzy's that started ticking when the master switch was turned on, but I can imagine that some dodgy operator might try such a trick.
Last edited by Unhinged; 27th Apr 2009 at 08:08.
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Over the years we've found that for each 100 maintenance hours (tacho or airswitch) you get around 110 VDO hours. Costings done accordingly, so if you want to hire on airswitch then be prepared to pay about 10% more than VDO.
There are some VDOs that run on master switch, in which case the VDO time at start up is noted, sometimes the stude may have been sitting there listening to the ATIS for 10 minutes
while you do your secret instructors business prior to the flight...obviously they shouldn't pay for that.
There are some VDOs that run on master switch, in which case the VDO time at start up is noted, sometimes the stude may have been sitting there listening to the ATIS for 10 minutes
while you do your secret instructors business prior to the flight...obviously they shouldn't pay for that.
Once hired a 55 Baron where the airswitch was actually attached to the gear squat switch, which meant you only paid when the gear was up - very tempting to do lots of practice ILSes in that one! Even a normal airswitch is a much better (and fairer) proposition in high performance aircraft, especially if you are flying relatively short legs (where the taxi time is a bigger proportion of the total time). Plus - no incentive to rush to pre-take off checks and much less likely to get agro with ATC when they tell you to expect a 10 minute delay while on the ground at BK while SY DEP identifies and separates the VFR C152 that just departed into Class C in front of you!
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Mostly flying schools charge by VDO, if one is fitted. What works out cheapest all depends on what you're doing. On a Xcountry with the power well up in something like an Archer, tacho can actually work out more than VDO. After a session of circuits or stalls, tacho is usually up to 30% less than VDO, which usually starts counting as a result of oil pressure and so counts from start-up. Worse, some start counting as soon as the master switch goes on.... Airswitches I've come accoss, either work on the airspeed indicator, which starts counting beyond a certain speed, maybe 40 Kts, or have a small vane mounted outside somewhere that blows a microswitch shut when the airflow is enough. So, any self respecting owner/flying school would be nuts to charge by airswitch - but would almost certainly use that for the maintenance time. Another variation is the one that starts counting when the gear goes up. I once knew a guy who had one of those. Was OK until he took it for a 100hrly where they jacked it and rasied the gear - then left it up over a weekend. 
Charge by VDO, maintenance by airswitch - that's how they make money!
$215 VDO is less than some. 172's I know of vary from $160 - $245 VDO inc GST.
Charge by VDO, maintenance by airswitch - that's how they make money!
$215 VDO is less than some. 172's I know of vary from $160 - $245 VDO inc GST.
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How do you know?
I would like to know more about how aircraft hours are ascertained. Particularly variances in ttis hours and vdo hours. I dont understand or know a lot of the jargon but after reading the threads its seems I may learn something here. Any knowledge shared would be appreciated.
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There are a few main types of hour recording that you need to know about as the aircraft hirer (there may be other types or the method used to record them may vary depending on aircraft configuration).
1. VDO / Taco / RAW engine hours
Depends on aircraft configuration, however for some aircraft, starts to tick over when engine RPM exceeds threshold, for example, 1,500 rpm. As you can imagine, it will only tick over hours during runups, followed by takeoff and flight. Alternatively, some configurations start the hours ticking as soon as the engine is running. Engines with FADEC for example, start ticking over hours at 1,500rpm+.
2. Airswitch
Ticks over hours once the aircraft reaches a certain airspeed.
If you can hire an aircraft on airswitch time for a similar rate to VDO then you'll be laughing financially.
During circuits at an airport such as Bankstown or Moorabbin where it's often busy, the difference can be significant, at a rate of around 1.4.
1.0 hours airswitch.
1.4 hours taco / vdo.
Some owners feel that if the hirer is paying for the aircraft based on airswitch, then they are more likely to treat the aircraft well, for example, warm it up, don't over-rev it etc.
It is fair enough however, to be paying for VDO when an instructor in on board, otherwise expect the hourly rate to be higher for airswitch.
TTIS in the case of an advert for a used aircraft would normally be based on airswitch.
Unfortunately there is often debate in engineering / LAME circles where some feel that maintenance should not be performed on airswitch times, but rather VDO, as after all, the engine is still running for those hours. Compare to a car, oil change at 10,000 hours, but if a lot of those KMS are done in stop start or barely moving traffic, do you do the oil change at 14,000 kms instead?
1. VDO / Taco / RAW engine hours
Depends on aircraft configuration, however for some aircraft, starts to tick over when engine RPM exceeds threshold, for example, 1,500 rpm. As you can imagine, it will only tick over hours during runups, followed by takeoff and flight. Alternatively, some configurations start the hours ticking as soon as the engine is running. Engines with FADEC for example, start ticking over hours at 1,500rpm+.
2. Airswitch
Ticks over hours once the aircraft reaches a certain airspeed.
If you can hire an aircraft on airswitch time for a similar rate to VDO then you'll be laughing financially.
During circuits at an airport such as Bankstown or Moorabbin where it's often busy, the difference can be significant, at a rate of around 1.4.
1.0 hours airswitch.
1.4 hours taco / vdo.
Some owners feel that if the hirer is paying for the aircraft based on airswitch, then they are more likely to treat the aircraft well, for example, warm it up, don't over-rev it etc.
It is fair enough however, to be paying for VDO when an instructor in on board, otherwise expect the hourly rate to be higher for airswitch.
TTIS in the case of an advert for a used aircraft would normally be based on airswitch.
Unfortunately there is often debate in engineering / LAME circles where some feel that maintenance should not be performed on airswitch times, but rather VDO, as after all, the engine is still running for those hours. Compare to a car, oil change at 10,000 hours, but if a lot of those KMS are done in stop start or barely moving traffic, do you do the oil change at 14,000 kms instead?
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In simple aircraft like fixed gear singles, the owner will do maintenance on tacho time - most tachs in these are set to match watch at 2300rpm, and because the owner is doing his /her maintenance on this system, then thats what the a/c hire in/out rate should be based on (fuel burn is also directly proportional to RPM).
Most of these simple a/c on crosshire are also fitted with a VDO running off either oil press or master, for the purposes of easily recording the time an instructor is sitting in the RHS. In either event, during circs VDO will be about 10-20% ahead of tach, and on a crosscountry at 75% power VDO and tach will be the same.
For reasons stated before, training/endorsements at reputable outfits will be on VDO, and PVT hire on tach.
The charge in method is negotiated with the owner (at least with X/hired a/c) at the time of putting the machine on line.
More complicated aircraft are another story - generally the way the owner does maintenance should be the way the a/c is hired in/out - instructor time always being master on to master off.
Most of these simple a/c on crosshire are also fitted with a VDO running off either oil press or master, for the purposes of easily recording the time an instructor is sitting in the RHS. In either event, during circs VDO will be about 10-20% ahead of tach, and on a crosscountry at 75% power VDO and tach will be the same.
For reasons stated before, training/endorsements at reputable outfits will be on VDO, and PVT hire on tach.
The charge in method is negotiated with the owner (at least with X/hired a/c) at the time of putting the machine on line.
More complicated aircraft are another story - generally the way the owner does maintenance should be the way the a/c is hired in/out - instructor time always being master on to master off.
instructor time always being master on to master off.
What about preflight briefing?
What about post flight debriefing?
How about a new student being shown how to perform a preflight inspection?
Should the instructor pop out to the flight line and turn the master on before beginning any of those?
It never seemed to be an issue in the past, pretty much everywhere I flew you had a dual rate and a hire and fly rate for the aircraft. All on tach time. The reason for the Hobbs in twins is that most of them don't have hour counters in the tachometers.
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A guy at my work went with a mate years ago for a jolly in a twin from Essendon. All he remembered from the flight was taxiing out whilst nursing the dash in his lap with a disconnected hour meter.
Never seen one like Buzzy's that started ticking when the master switch was turned on, but I can imagine that some dodgy operator might try such a trick.
I went to the same aero club, which is based at an International Airport. I can just imagine a long taxi, holding for a few jets before being cleared for take off. Could easily imagine a 20 minute charge sitting idling. I have not been back
Just to stir muddy water. VDO is a brand of instrument. Hobbs is also a brand of instrument.
Either brand of gauge can be wired to run when:
1. The battery master is turned on.
2. The oil pressure rises.
3. The gear is retracted.
4. Weight on wheels (squat) switch.
5. Airswitch.
The point is made above that the rate you pay will reflect the method used.
Saying something is charged as "VDO" does not define the method used to switch the meter on.
Either brand of gauge can be wired to run when:
1. The battery master is turned on.
2. The oil pressure rises.
3. The gear is retracted.
4. Weight on wheels (squat) switch.
5. Airswitch.
The point is made above that the rate you pay will reflect the method used.
Saying something is charged as "VDO" does not define the method used to switch the meter on.
