Category: Tech Log

It has been five months since G-EJBI last flew and time to hurry up and finish the annual inspection. I am tending to do the work myself with Andrew which is then checked by a local CAA engineer. A local maintenance organisation then reviews the work and issues the ARC certificate. This was all completed mid May and G-EJBI was back flying. My initial impression of the fixed pitch propeller is very favourable with little change to the aircraft performance.

Back in January I realised that a new spinner and attachment plate would be required for the fixed pitch propeller. All the drawings for these parts are available on Claus’s excellent website www,boelkow207.de  A firm in Norfolk, who initially seemed keen to fabricate the spinner, eventually admitted defeat when their toolmaker was unable to supply the former to spin the alluminium around. A local engineering firm were going to make the attachment plate and reuse the original spinner but with covid delays I eventually got cold feet, worried about possible ballance issues.  I have now ordered an RV alluminium spinner, not technically the correct solution but should loosely qualify as an owner fabricated part and suffice while I sort a more ‘correct’ solution.

Having modified the engine it was time to fit the ‘new’ propeller. I say new but G-EJBI’s new prop is around 20 years old. There is not a lot of U.K. prop stock and what is available is quite pricey. There are also  waiting times and delivery costs if importing from the States. I was offered a new but old stock propeller at a reasonable price so that seemed the way forward. Included in the price was an overhaul and fresh paint, it should be good for 2000 hours. The Sensenich propeller fits straight on the hub, which as there is no CSU, places the blades a little further back.  This causes a slight problem as the blades are now very close to the lower cowling and the spinner attachment ring is not usable.

An original option with the Bölkow 207 was to have a Sensenich fixed pitch propeller fitted. Not as cool as a constant speed prop and with a performance defecit, I figured it was only a bit less cool and the performance was only marginally poorer. I set about removing the propeller governor with it’s adapter and installing a blanking plate. The oil line is removed, the rear crankshaft plug pierced and a new front plug installed. The engine is now to Lycoming O-360 A2A specification which is a requirement for the fixed pitch prop.

The O-360 engine with a 72″ Hartzell prop is a fairly popular combination but try as I might, I could not find a suitable second hand item. MT Propeller in Germany manufacture a three blade composite prop with the required approval for the 207. It is reassuringly expensive and there would be a three month wait for delivery. I spoke with an owner who had recently fitted the MT prop to his 207, he was very satisfied with the results, particularly the smooth running. I was not so sure the benefits justified the £13,000 price, there must be an alternative and hopefully cheaper solution.

Our Hartzell propeller was sent to the Prop Shop and unfortunately was found to have corrosion on the hub. This was not repairable as no machining is permitted on this component. A replacement hub would have to be specially made by Hartzell and would cost an awful lot of money. A new 2 blade Hartzell propeller which would fit and work perfectly was also not an option as the new model had an alluninium hub, a different serial number and hence no approval for the Bölkow 207.

Having extended the time between overhaul of the propeller by operating on condition, it now seemed prudent to have the prop off and sent to a repair shop for a thorough inspection. The Bölkow 207 is normally fitted with a steel hub Hartzell constant speed prop. The fact that this steel hub model is the only Hartzell prop specified by the airworthiness authority that may be fitted to the 207, is about to cause me a few problems.

At the end of 2019 we performed the 100 hour check and annual inspection. I finally managed to install the schrader valves on to the oleo struts. Other jobs were fitting a new heater manifold, beautifully made by Competition Fabrications of Attleborough and a spray paint job on the front cowling performed by a local car spray workshop. Mainly due to the weather it would be February before G-EJBI’s next flight.

G-EJBI has flown around 40 hours so far this year but with the last check being in December, it was time for a 50 hour check. Andrew and I for the first time felt confident enough to perform the work ourselves without supervision from an aircraft engineer. One job was to re-route the oil breather pipe, it had been interfering with the cowl flaps preventing them from fully closing. I still stick with W80 oi, maybe one day I will change to multigrade.