A good reminder to always treat props as 'live'
As with so many other areas of aviation, hand starting engines is one in which a detailed understanding of the specific fuel and ignition system fitted to the specific aircraft is essential for success and safety. AB touched on this issue earlier, when he said:
If your aircraft is fitted with e.g. an injected Conti and the only way to prime it is an electrical auxiliary pump, it's going to take an enormous amount of hand swinging to get that baby started if the battery's so dead that it won't run the aux pump to prime it. At hand swinging RPMs, the EDP isn't doing much at all. (The last time I hand started an IO520 the battery still had enough charge to run the aux pump slowly, but sufficiently to prime the injection system. As noted by currawong, they start easily when swung. Very - and dangerously - easily. But only when the F:A in the induction system and the spark are correct. Speaking of the spark....)
Some ignition systems use retard breakers in the magnetos and electric aids to starting, like "Shower of Sparks" vibrators and 'SlickStart' boosters. They have complicated wiring at and from the ignition switch. That wiring is different than if the magnetos each have just a mechanical impulse coupling. The electrically boosted ignition circuits are rarer these days - at least on 'traditional' GA piston engines - but not extinct. Trying to hand start one of those engines with a flat or low battery may be, at best, impossible, and at worst, deadly, no matter how competent you are at hand swinging in general. And note that the generic model of the same engine can have different magnetos and start systems. Not all e.g. IO520s have the same ignition systems.
For my part, I listen for the 'snap' of mechanical impulse couplings unwinding in both magnetos, while pulling the prop through slowly (with the mags off but assuming they are 'live'), before attempting a hand start. I'm not aware of any esoteric starting aids that still retain mechanical impulse couplings in the magnetos.
....Continental powered seaplane, look at the panel and note the manual plunger primer. Then ask why it is fitted.
Some ignition systems use retard breakers in the magnetos and electric aids to starting, like "Shower of Sparks" vibrators and 'SlickStart' boosters. They have complicated wiring at and from the ignition switch. That wiring is different than if the magnetos each have just a mechanical impulse coupling. The electrically boosted ignition circuits are rarer these days - at least on 'traditional' GA piston engines - but not extinct. Trying to hand start one of those engines with a flat or low battery may be, at best, impossible, and at worst, deadly, no matter how competent you are at hand swinging in general. And note that the generic model of the same engine can have different magnetos and start systems. Not all e.g. IO520s have the same ignition systems.
For my part, I listen for the 'snap' of mechanical impulse couplings unwinding in both magnetos, while pulling the prop through slowly (with the mags off but assuming they are 'live'), before attempting a hand start. I'm not aware of any esoteric starting aids that still retain mechanical impulse couplings in the magnetos.
Last edited by Lead Balloon; 9th Jan 2016 at 20:50.
The Rotax 912 Operators manual requires that the propeller be rotated by hand to build up compression in the crankcase to force oil into the oil tank. You do this until you hear the engine oil tank "burp". You then check the dipstick.
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What step of this "mandatory way" magneto timing is remove vacuum pump?
http://www.tcmlink.com/pdf2/msb94-8d.pdf
The prop is required to be turned backwards.
Turn the propeller slowly in the direction of normal rotation until the piston lightly
but positively touches the TDC locator.
4. Rotate the disc of the timing indicator until 0 degrees aligns with the pointer. A light
tap of the finger against the dial will ensure that the pointer is centered.
5. Slowly turn the propeller in the opposite direction of normal rotation until the piston
lightly but positively touches the TDC locator.
http://www.tcmlink.com/pdf2/msb94-8d.pdf
The prop is required to be turned backwards.
Turn the propeller slowly in the direction of normal rotation until the piston lightly
but positively touches the TDC locator.
4. Rotate the disc of the timing indicator until 0 degrees aligns with the pointer. A light
tap of the finger against the dial will ensure that the pointer is centered.
5. Slowly turn the propeller in the opposite direction of normal rotation until the piston
lightly but positively touches the TDC locator.
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De Rated, Band a Lot
The PPrune search function reveals that the same points were being made in 2006 with some suggesting dire consequences to the vacuum pump if rotating the prop backwards with others pointing out that rotating the prop backwards was standard practice when setting ignition timing, presumably with no damage to vacuum pumps.
For a specific set of circumstances: Cessna 172 with cold engine (first flight)- if we rotate prop backwards by hand is it possible to cause damage to engine or engine components ?
The PPrune search function reveals that the same points were being made in 2006 with some suggesting dire consequences to the vacuum pump if rotating the prop backwards with others pointing out that rotating the prop backwards was standard practice when setting ignition timing, presumably with no damage to vacuum pumps.
For a specific set of circumstances: Cessna 172 with cold engine (first flight)- if we rotate prop backwards by hand is it possible to cause damage to engine or engine components ?
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An engine can run backwards by itself, to a small degree, when it hits compression as it stops spinning, on shutdown.
So the suggested component damage (such as to a dry vacuum pump) being caused by turning backwards - at first glance, doesn't seem likely - as one would expect engine manufacturers would have taken this into account in the design of components.
However, the CASA airworthiness bulletin below, is very pointed about the dangers of possible dry vacuum pump damage, due to rotating an engine backwards.
You will note that the vanes in the dry vacuum pump are angled, unlike many vacuum pumps, and they are designed to run in one direction only.
As they run dry, relying only on lubrication from graphite dust from the vanes themselves, it is immediately obvious that the chances of vane damage caused by reverse rotation, over more than a relatively low number of degrees, are high.
CASA Airworthiness Bulletin 37-003 - April 2015
So the suggested component damage (such as to a dry vacuum pump) being caused by turning backwards - at first glance, doesn't seem likely - as one would expect engine manufacturers would have taken this into account in the design of components.
However, the CASA airworthiness bulletin below, is very pointed about the dangers of possible dry vacuum pump damage, due to rotating an engine backwards.
You will note that the vanes in the dry vacuum pump are angled, unlike many vacuum pumps, and they are designed to run in one direction only.
As they run dry, relying only on lubrication from graphite dust from the vanes themselves, it is immediately obvious that the chances of vane damage caused by reverse rotation, over more than a relatively low number of degrees, are high.
CASA Airworthiness Bulletin 37-003 - April 2015
Interestingly, the recommendations in the AWB do not include one to the effect: "Don't move the propellor in the opposite direction to normal rotation", despite reverse rotation as being mentioned as one possible cause of damage to vane-type vacuum pumps.
If you do the calculations on how much reverse rotation a vacuum pump would 'suffer' during a normal timing check or other ground handling activity, that's not surprising. If those pumps are indeed that delicate that they'd suffer damage at ultra-slow rotation a few tens of degrees in the opposite direction to normal rotation, they shouldn't be fitted to aircraft engines in the first place (or there should be a big placard in the cockpit and in the POH and the maintenance manuals that says: DON'T EVER ROTATE THE PROPELLOR IN THE OPPOSITE DIRECTION TO NORMAL ROTATION
If you do the calculations on how much reverse rotation a vacuum pump would 'suffer' during a normal timing check or other ground handling activity, that's not surprising. If those pumps are indeed that delicate that they'd suffer damage at ultra-slow rotation a few tens of degrees in the opposite direction to normal rotation, they shouldn't be fitted to aircraft engines in the first place (or there should be a big placard in the cockpit and in the POH and the maintenance manuals that says: DON'T EVER ROTATE THE PROPELLOR IN THE OPPOSITE DIRECTION TO NORMAL ROTATION
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Not one to put much into CASA AWB's (I love the compass one!) THERE ARE A NUMBER OF THEM THAT SIMPLE GET REMOVED/CANCELLED.
If the reverse rotation of prop were true for vac pumps, then most failures should be during or on ground run after 100 hr maintenance, where doing timing of mags requires reverse rotation of prop a little or a lot. If the vane was to chipped then it will self destruct on start up (contamination).
Most vacuum pumps DO NOT fail at this time not from my experience within an hour or 3 after timing check regardless of starts.
I have noticed over the years that when there is more smoke around from bush fires there seems a lot of vac pump changes happening, also if a vac pump is swapped at engine change it fails soon after within 50 hrs often.
If the reverse rotation of prop were true for vac pumps, then most failures should be during or on ground run after 100 hr maintenance, where doing timing of mags requires reverse rotation of prop a little or a lot. If the vane was to chipped then it will self destruct on start up (contamination).
Most vacuum pumps DO NOT fail at this time not from my experience within an hour or 3 after timing check regardless of starts.
I have noticed over the years that when there is more smoke around from bush fires there seems a lot of vac pump changes happening, also if a vac pump is swapped at engine change it fails soon after within 50 hrs often.
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"For a specific set of circumstances: Cessna 172 with cold engine (first flight)- if we rotate prop backwards by hand is it possible to cause damage to engine or engine components ?"
On the camber in the vac pump, that is at the vent fitting and exposed to the atmosphere in a tropical upto 90% each day. How is the rust on the steel wall of vac pump after 29 days standing and still cold on said C172.
On the camber in the vac pump, that is at the vent fitting and exposed to the atmosphere in a tropical upto 90% each day. How is the rust on the steel wall of vac pump after 29 days standing and still cold on said C172.
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Many aircraft have only have an impulse coupling on one of the magnetos.
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Little point in hand starting an alternator equipped aero engine if the battery is flat, as the alternator requires excitation to come on line. No radio, no navaids, no lights and maybe no flaps or undercarriage. However I understand that the GA-8 Airvan has a battery in the alternator circuit to provide the initial excitation.
Assuming the battery is OK and just run flat by say leaving the master on, it will quickly regain enough power to excite the alternator simply by leaving it with zero load for 10 or so minutes.
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Why have magneto (independent ignition source) in fact why have 2? Aircraft are and must count on battery failure and still fly.
Rumour has it they can also start with out a working starter system and still fly, even if one magneto fails rumour is it can still fly all be it less power on most occasions.
Fact is a engine can and will start even if TCM forget to put both impulse couplings on a Barron engine. It was only notice at a routine removal and started like a champ each and every time from factory NEW.
Rumour has it they can also start with out a working starter system and still fly, even if one magneto fails rumour is it can still fly all be it less power on most occasions.
Fact is a engine can and will start even if TCM forget to put both impulse couplings on a Barron engine. It was only notice at a routine removal and started like a champ each and every time from factory NEW.
Fact is a engine can and will start even if TCM forget to put both impulse couplings on a Barron engine. It was only notice at a routine removal and started like a champ each and every time from factory NEW.
No impulse couplings and no retard breaker circuits?
Bendix or Slick mags?
Many aircraft have only have an impulse coupling on one of the magnetos.
S'pose so. The starter motor is rotating the prop a little quicker than a hand swing.
Band a Lot may be able to answer this: How many degrees advance on the magnetos fitted to those Baron engines? I thought 22 or maybe 24, but that's just a guess.
Band a Lot may be able to answer this: How many degrees advance on the magnetos fitted to those Baron engines? I thought 22 or maybe 24, but that's just a guess.
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Bendix,
Willie, Hannas, Noel, Aaaron and a few others can confirm. Out of box from TCM to Kalahari Air Services - company policy their to remove and check mags each 100 hrs.
22 degrees.
Noel I think still current owner, call and ask him he will confirm. (smart guy remembers lots).
Willie, Hannas, Noel, Aaaron and a few others can confirm. Out of box from TCM to Kalahari Air Services - company policy their to remove and check mags each 100 hrs.
22 degrees.
Noel I think still current owner, call and ask him he will confirm. (smart guy remembers lots).
Last edited by Band a Lot; 11th Jan 2016 at 08:18. Reason: answer Q
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Most accept there is some risk if an amateur attempts to hand prop without instruction. Even Aussie Bob, the expert pilot from the Bush alludes to that fact.
Question without notice. If an aircraft flat battery is discovered, is it possible to undertake a "jump Start" from a car if one is handy, rather than taking the risk of becoming a one-armed wall paper hangar?
Question without notice. If an aircraft flat battery is discovered, is it possible to undertake a "jump Start" from a car if one is handy, rather than taking the risk of becoming a one-armed wall paper hangar?
Most accept there is some risk if an amateur attempts to hand prop without instruction. Even Aussie Bob, the expert pilot from the Bush alludes to that fact.
Runaway aeroplanes aside, has anyone ever heard about anyone hurting themselves doing this operation? I haven't but I guess there are some.
Moving on to the jump start though, no problem at all. With three leads and two cars, even a 24 volt blat flattery can be fixed this way.
I should add as an afterthought here though, on some types it can be a wee bit tricky getting the cowl back on with the engine running.
Last edited by Aussie Bob; 11th Jan 2016 at 18:33.