Friday 24 May 2013 09:04 UTC
The place for technical discussions about GA and flying.
Technical discussions about GA only, please.
Okay, so someone on the GA board (golfcharlie) mentioned the little-known Potez engine found in some Jodels and Emeraudes.
He also mentioned they are rather cheap as no-one knows about them (and I recall an advert from Mike Hallam offering one for about a grand so I know he's right!)
Now, I know nothing more about engines than the basic PPL course taught me (i.e. barely anything and some of that wrong).
Since Potez have long since vanished and the overhaul company (GMP Potez) also appears to be no more, I am wondering how one would go about carrying out an overhaul of a "time-expired" Potez. Granted there is no such thing as time-expiry on a permit, but you know what I mean!
Presumably there is a limit to the number of times the engine can be rebuilt and parts repaired rather than replaced? I can't imagine it is simple or cheap to machine from scratch e.g. a whole new block, so is it a case of finding spares and hoarding them? Or am I missing something really obvious?
This is of slightly more than academic interest since I'm currently trying to track down a Jodel to purchase so it would be good to know how risky a Potez buy would be.
Thanks in advance for anyone willing to share their knowledge with an ignoramus like me ...
Regardless of how good or bad a Potez engine might be, the aircraft they're fitted to seem to be devalued quite markedly. If you buy one for a bargain, expect to sell it cheaply should you ever decide to.
Go to http://www.jodel-fr.com/ and you will find in this forum many fans of Jodel with Potez engines.
You will find also all the support you need from advices to spare parts.
This engine is really more "dynamic" compare to contienetal O200. Talking just about the flight and performances it is far beter than O200.
But the time before overall is less and the ignitionis definitely not so good compare to the slick or Bendix magnetos.
But in France the price of one plane is not really lower if fitted with Potez compar to Continental.
For example a DR 1050 in correct condition is around 25 000 to 30 000 Euros. Many of them ( DR 1051) are fitted with Potez and price is same.
Note also that the engine fixation points are same on Continental and on Potez. so you can change from one to the other without any other modification.
GMP Potez was operated by my friend Charles Ollivier, who sadly died 18 months ago. Charles built or rebuilt no less than five Jodels, each one Potez powered. Before he retired, he ran a small Renault dealership/maintenance business near La Rochelle. He was a lovely man, and everything he touched with his hands were the work of an artist: whether Potez engines or Wood. Charles used to rebuild (zero life) Potez engines, using either the owner's servicable components, or where possible, new components he sourced on his own initiative. He could supply new pistons and cylinders, which he ordered in small batches from the original manufacturer. Likewise main crankshaft bearings.
Charles was a talented natural self-taught engineer. He designed an built modifications for the Potez and obtained the DGAC Approvals.
In it's original guise, the Potez had undoubted weaknesses, but as modified by Charles it is a super engine. He used to maintain Potez engines for the likes of me for mini-money. He zero-lifed and brought my Potez to its current as-new state for (if I remember correctly) about 6,000 Euros. That gave the engine (under DGAC rules) another 1375 hr. Under LAA 'on condition', it should see me out. It runs on 95 Mogas, still available in some parts of the West Country. In France, they use 'Super' straight from the pumps. No problems reported (that I have heard of).
1. Removal of heavy rear-mounted Ducellier starter motor; close off hole in crankcase.
2. Removal of heavy front-mounted Ducellier generator.
3. Insertion of starter ring on crankshaft front-end: installation of lightweight automotive starter and actuator at front end.
4. Removal of Ducellier double-banked distributor from rear of crankshaft: split crankcase, machine inside, new bearings, installation of Slick/Bendix mags.
5. Installation of oil cooler on front firewall.
Outcome: no weight gain; no change in C of G. Fabulously easy starting, even in winter (I am the world's most experienced prop-swinger; no more!). This engine is rated at 105 hp, but if properly set up (e.g. Pierre Robin and the Round Sicily Air Races) it is probably giving 115 hp.
In a Jodel Sicile Recorde, on a normal day it will haul three adults and 60 litres of fuel + a bit of personal baggage out of a 600 yard strip, no problem. Given a hard runway, 4 x 75 kg POB is do-able.
If you are considering buying an aircraft with the Potez, it will probably come with some spares. All owners keep some, and there is an informal support swap network between Potez owners. But the mutual support and the friendships which arise, are half the fun. "You scratch my back, and I'll give you four exhaust gaskets."
In the UK the aircraft are (I think) all on an LAA Permit to Fly, and there is plenty of advice. I have never been grounded for want of spares in 20 years. So maybe I am just a touch biased.
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