Antique Airways Gipsy Engine Overhaul & Maintenance Tips
Antique Airways has CASA approval to overhaul and maintain the Gipsy four cylinder aero engine under the name of GIPSY AERO OVERHAUL
Gipsy Aero Overhaul is approved by CASA to carry out complete overhaul, top overhaul and bulk strip of the Gipsy engine.
My name is Warwick Woinarski, the name behind the Antique Airways And Gipsy Aero Overhaul.
I have owned and operated my DH82a Tiger Moth VH-BJE since 1973. At the tender age of 23 when I purchased BJE I knew nothing about how to maintain my aircraft. From an early age I was always interested in all things mechanical and so I set out asking questions. The learning curve at first was steep and in the early days I found myself in strange places with an engine either not running or running rough.
The Gipsy is a simple and reliable engine but it does have a few problem’s that if aware of will never cause concern but if left unattended will put you down.
Please be aware that what I am about to say is only my thoughts gained from 42 years of operating my Tiger. There is always two sides to a story and I have had many a long discussion with very respected engineers over certain points, not all agree,and I respect their views. What I do know is that I have been running my Tiger in joy flight operations for 20 years now doing approximately 300 hours a year and it runs like clockwork never ever giving me or my pilots concern.
To state the obvious regular maintenance is the key to stress free flying. For 39 years now I have followed the same schedule of maintenance. Each 25 hours I change the oil and clean the filters. (each 100 hours I clean the pencil filter in the magneto oil feed line) Check the contact breaker gap, clean the fuel filter, adjust the tappetts and clean the spark plugs. Also at each 100 hours I disconect the fuel line at the carby and turn on the fuel to check the flow, then I turn off the fuel and remove the two jets to check for water or sediment. Then before replaceing the jets I turn on the fuel and flush the carby.
The Hobson carburettor fitted to the Gipsy gives very little trouble,but the float does require some attention. When set up and running the carby needs very litle attention other than routine checks as mentioned, but the float can cause a few problems. Over time the dope coating on the float can develop cracks and the cork starts to absorb fuel and become heavy. The first sign of this is usually a hard to start engine due to a high float level. A few years ago here a Tiger Moth was damagaged beyond repair as a result of a forced landing,the float was fuel soaked and had expanded jamming against the sides of the float chamber with the needle on the seat so no fuel could flow and the noise stopped. On the subject of fuel, MOGAS will not affect the dope coating ( I have put two cork floats, one each in a seperate sealed jar and filled one jar with AVGAS the other with MOGAS, left them for a few months. The result both corks looked the same, the coating not effected by either fuel type). With the bronze heads I run only MOGAS,with Marvle Mystry oil as an upper clyinder lubricant and fuel cleaner,it works. The manual states use a good quality motor spirit . This is a subject that will be argued till the end of time.
The weak area of a Gipsy is the Cylinder heads. The Gipsy engine will run its full overhaul period but the top end or the bottom end as it is upside down needs regular attention. The main problem is the exhaust valves with only 25 pounds on the seat they tend to burn out in approximately 200 to 300 hours sometimes even less depending on the fuels used and the RPM. I have been using a upper cylinder lubricant which has helped. The Gipsy engine was developed in an era when engines were designed to run flat out, they were tested way beyond normal RPM and then derated. The Gipsy engine does not like to be babied, by this I mean operated with with kid gloves. I have always had respect for my engines so I warm them up open and close the throttle gently, this all helps but I also run at 1950 to 2000 RPM and occasionally give it a gallop at 2100 which is max cruising RPM.(240 for a 10mk II)
Whilst on the subject of exhaust valves it is important to note that if you have the so called training valves (part n# 1902-23) in your engine, they have a short life before the heads pops off and causes major damage to the engine, not to mention the airframe if it happens over the wrong terrain for a successful forced landing. Training valves were produced in great numbers and so they are easy to get hold of and are approved, but are of poor quality. The problem is that they run OK for about 300 hours before they give trouble so I would recommend they be replaced between 250 -300 hours, the closer to 250 the better. Inlets never give any trouble.
These engines were designed to run on unleaded fuels in fact at first they ran on 70% octane white spirit. Leaded fuels were introduced to burn better in high performance engines such as the Merlin V12.
Fuel is a major contributor to the life of the valves, the type of fuel that you should use will depend on the MK of Gipsy you are running and who you talk too, believe me this will be a subject that many will never agree on . Personally I find that the use of AVGAS is detrimental to exhaust valve life. There are many engineers that will argue that you should only use AVGAS as it is a the approved fuel for use in aircraft. Gipsy engines with alloy heads such as the1f/c and mk10 engines can handle Tetra-ethyl lead (T.E.L.) AVGAS. The manual states The use of fuels containing up to a maximumof 4ml T.E.L per imperial gallon is permitted, but the limiting clyinder temperatures are adjusted in consequence. I have found engines running on AVGAS tend to have a short valve life, this is because AVGAS burns slowly and is still burning when the the valve is closing .
Also the manual states The Gipsy Major 1 has bronze heads and must not be operated on fuels containing T.E.L. The reason is because the lead eats away at the bronze especially around the valves seats.
This bronze head is showing sings of deterioration around the exhaust seat caused by using leaded fuels. Gipsy engines with bronze heads are not permitted to use fuel containing more than 4% lead.
The seat gets eroded away by the lead and drops out causing massive damage to the head.
In all the years I have been aroung Gipsy engines there are two things that tend to cause problems. One is the valves and the other is the magnetos.
Magnetos are like light bulbes one minute they work the next they dont. I do not how many times I have checked the mags on shut down and all is OK only to find the impulse maggy dead next time I go to start. It always pays to have a spare set in the hanger. The problem with keeping a spare set is they do not like lying around and if moisture creeps in the they die just sitting there.Magnetos are best stored in a dry sealed container ( if possible in a warm cupboard say near the hot water system)
I have changed over to Slick magnetoes which have a STC for the Tiger Moth and Chipmunk. No more sticky impulse it starts each time, runs better, burns less fuel, no mag drop and even looks like they were made for the engine. The conversion is simple to install less maintenance with greater reliability.
Remember what I say is only my observations and not to be taken as gospel as not all agree
Oil is an interesting topic and one that many will disagree on. 99% of operators use a straight oil because most of us are of the belief that is what the manufacture requires. Some say that the modern oils are not designed for the Gipsy which is a bit like putting the cart in front of the horse.
There has always been a long standing discussion about running engines in on straight oil and if you have a modern engine like a Lycoming or Continental then the recomendation is after 50 hours change to and ashless dispesant or detergent oil.
I am very keen on anything with an engine and have a Vintage motor cylce and a hot rod, I guess you can say engines are in my blood. All my vehicles run on detergent oils from day one and that includes my Tiger Moth.( not all will agree but I have had nothing but success)
Straight oils are OK and will cause no harm execpt that they run dirty after a while build up sludge and clog the piston rings, none of which will put you down but will degrade the life of the engine and its performance.
There is a ring mod out that uses a different type of oil ring in an attempt to reduce the oil consumtion. this ring mod is OK and it does help but not always, I have known engines with the mod and no difference to oil cosumption.
Straight oil gums up the very small holes in the piston behind the oil ring, the rings themslevs gum up and can no longer perform their function, the oil gets past and burns in the combustion chamber.
Detergent oils keep the engine clean and do not build up sludge. The difference in engines that run detergent oils as opposed to those that don’t is very noticable when stripped down for overhaul.
I do not have the ring mod on my engines and run Shell W120, at overhaul they are very clean, also my oil consumption remains very low. Instead of a litre an hour which is acceptable for a Gipsy I get more like a litre every 2.5 hours.
Last Updated (Wednesday, 08 June 2016 00:44)