[LZ791]

I am recently qualified for my PPL and am now thoroughly enjoying my flying. My usual steed is a 152 or Pa 28 Warrior. On one of my final dual 152 flights before qualifying we flew into Southend for a tour around the control tower and to spend time with ATC. All went well with an enjoyable forty minutes or so watching comings and goings. Pre flight checks completed we lined up on the easterly heading and took off. Shortly after and less then a minute into the climb I mentioned to my instructor that I felt the climb rate was poor compared to usual. ATC then came on asking if all was ok as from the tower we looked quite low compared to the normal climb rate they view from their elevated perch! A quick panel scan T's & P's where they should be, primer locked, odd! Mags have you checked the mags said my instructor!! Sure enough on doing the engine run up and mag check muggins here had somehow not switched back to right, we were running on just the left mag. Turning the key one notch to the right had the instant desired effect, normal climb rate was resumed.

I felt a fool, I had never done this before and wondered to myself would I have found the problem on my own? It goes to show how easily a little lack of concentration or distraction can cause a potential
incident, pretty sure it was the Easyjet heavy that departed before us that took my attention away from completing this vital check correctly, that's no excuse I know.

Certainly plenty of attention paid now to mags. One can never over check, but you can regret not over checking!!

[aluminium persuader]

You know how when you turn the key in your door at home, if you hold the key at the "open" position it feels just a little unnatural?
When I'm doing the mag checks in a key-operated a/c, I never let go of the key until the checks are finished. Thus I go from "both" to "L" to "both" to "R" to "Both", and only when the key is back at the hard-stop right-hand does my wrist come back upright and I release the key.
The only caveat is that I am a pianist and left-handed and do the mag checks with my left hand so it may make me more sensitive to the position of my wrist.

[Gertie]

A quick panel scan T's & P's where they should be, primer locked, odd!

Need to scan all engine instruments and controls, fuel, mixture, the works. Primer locked is a good one - wasn't in one check list I used to use, so added it for myself.

I scan bottom right (fuel selector) round in an arc to the left ... and when involved in a real partial engine failure with an instructor that's exactly what he did too, and we both found the problem at the same time.

[johnm]

A good habit is to touch and look at all the items in the check list. That way when you do the mags on both check, your hand leads your eye to see where the key should be.

[riverrock]

I'd have thought that the difference in power output between 1 and 2 mags wouldn't be significant. When doing power checks, the RPM change is very small. How much less power would you expect the average (if there is such a thing) engine produce under one mag?

[leiafee]

It's a good 100-150 RPM on most stuff I've flown - not sure what that equates to in power but it's certainly distinctly noticeable.

[Neil MacG]

I'd have thought that the difference in power output between 1 and 2 mags wouldn't be significant. When doing power checks, the RPM change is very small. How much less power would you expect the average (if there is such a thing) engine produce under one mag?

I've had a mag failure in the Auster and while straight and level flight could be maintained while Carb Heat was not being applied, the application of carb heat + single mag drop meant we could not maintain height. Fortunately we were not far from the field and no permanent harm to aircraft of persons ensued. But we did ensure to keep a bit of extra height on approaching the airfield in case it should become a glide approach!

But whether it is an issue probably depends on normal performance of the aircraft. 500fpm climb in the Auster is the best you are likely to get on the 108hp up front on a cold winter day. 300fpm is much more normal so it's not so much a matter of how much less performance on a per mag basis, but what is the normal performance of the aircraft in the conditions.

And the mistake of not having the mags on both is very easy to make - especially in elderly Cessna/Piper aircraft where the mags are just another notch in the starter arc. One of the more postive aspects of the Auster is the separate lever switches for each mag makes it easy to see if either one is not in the correct position.

Neil

[PeteSpencer]

Think about it: Something good came of your error in that you'll never take off with one mag again.............

[ROG]

We learn by our mistakes---always ask your buddy to look to see if you miss anything--even when you"ve got thousands of hours.
Last year someone took my attention before taking off from a short strip as I was about to put flaps down-so didn"t----result thought this is odd not coming off--scraped over hedge. Thought --I shan"t do that again--use of flaps crucial for strip flying in this particular machine.
Yet to meet the pilot who"s never made an error.

[Flyingmac]

I flew into a farm strip for an overnight stay. On departing the next day, the temperature had climbed to 32C and the headwind I'd had on arrival had gone.

I watched a similar aircraft to mine get airborne with a hundred metres to spare.

I cleared the hedge at the far end by five or six feet with the stall horn chirping, (but not wailing) and went between trees that I should have gone over.

As I clawed my way skywards, my wife commented on the take-off being a bit tight.
I told her it was down to the heat, then distracted her attention while I quickly shoved the carb heat in. I still haven't confessed.

[Awqward]

I felt a fool, I had never done this before and wondered to myself would I have found the problem on my own?

If you apply the same technique whenever there is something not quite right with power:

F - Fuel (pump, selector, tank)
C - Carb heat
M - Mixture
I - Ignition (ie Mags)
T- Throttle (it may have vibrated back or you may have bumped it)

You should pick up most things with FCMIT in those first few seconds / Minutes

[Squeakmail]

A CAA staff examiner recently told me that it was perfectly acceptable to take-off with only one mag working.

He actually criticized me for saying that I considered both mags should be running normally, and within the tolerances published in the PoH, before I would deliberately take-off.

Is somebody here saying he was wrong?

[Keef]

Is somebody here saying he was wrong?

Yes!

[LZ791]

Well I sure as hell wont be trying that idea again! Has anyone tried this deliberately?? Its hard to describe the performance loss climbing out on one mag, sufficient even for the tower to call us and ask if all was alright! Back to both was like an injection of nitrous a HUGE difference. Granted it was a humble Cessna 152 I imagine it would be a similar scenario in other light singles.

[Sir Morley Steven]

Hi Mike. There's an easy way of never doing that again.
In the mag check, turn the key back two places to check the right mag first. Then when you do the second mag, it's only one place back and you have to put it back to both.

Then, of course, include a visual check on the mags in the pre take off checks.