Enstrom quirks and advice
For new Enstrom owners and prospective owners.
As a 6000 hour Enstrom type experienced pilot with ownership going back to the mid 1970s, I thought I might be able to help with some of the various vagaries of Enstrom type ownership threaded above.
Rotor Blades: Yes, many of the earlier MR blades suffered various problems. The leading edge 'flaking' mentioned above is called 'exfoliation' being a form of inter-granular corrosion. The factory stainless steel leading edge tape is a good preventative as is the earlier 3Ms polyeurothene (spelling!) tape. Best applied in short lengths so that the offending portion can be removed easily. IF the tape comes adrift in flight, yes it can cause a fierce vibration and the fix is simply to land and remove the tape. Only happened to me twice in 40 years and both times following continued flight in heavy rain. The factory service letter does allow leading edge re-profiling iaw the factory approved figures. Currently there is no fix for long (over 3 inches) leading edge voiding ... Neither is trailing edge bond separation repairable although I have seen rivet repairs which are not approved in CAA land. If in doubt ask your local AME about the 'tap test' for rotor blade serviceability.
Overheating: The Lycoming 360 is nicely cowled but in older engines with poor mixture set up will often overheat in prolonged, high power hovers at highish ambient temperatures. I think there is a fix by having two oil coolers. Due to cowling the problem is self perpetuating so as the temps get higher, they tend to progress in that direction. In fact in prolonged hover training, it is often necessary to move into a short period of forward flight to bring the CHT and oil temps down.
Mixture: The numbers provided above are OK, but special mention has to be made of the best EGT indications. The Lycoming E series turbo engine (280/28C models) produce the best power at 1550 degrees with 1650 allowing the best economy setting and thus range. Mixtures should only be leaned at MAP less than 29 hg. OR to 130 lbs per hour if indicating above that fuel flow. I teach leaning using the mixture vernier control at 28 MAP to give 85-90 lbs per hour. Normal when full rich can be anything up to 130 lbs per hour so a 40 lbs per hour fuel save is possible. (a little over 5 UK gallons!) and at the UK price of £2 per litre we are talking about a saving of £40-45 an hour!!!
Here's a thing to try. Set the Enstrom at 28 MAP, and accurately trimmed to straight & level, mixture full rich. Now lean as above. Observe the fuel flow reduction, the rotor rpm INCREASE and ditto the ASI by around 5 mph. A graphic indication of the mixture leaning requirement. BUT to new pilots NO LEANING until properly briefed by a qualified and experienced instructor.
Remember the boost light is there as an ' attention getter' to remind the pilot he is approaching the max 36.5 MAP boost figure.
Lamiflexs: When flying is done ... Never just dump the lever and go off for the weekend. This places a pitch 'set' on the M/R lamiflex bearing which hastens their demise and they come in at circa $1800 a copy. (three required!) Have the collective lever raised and locked in an approximate flying position to relieve the bearing load. Caution, new pilots might attempt to start on the next sortie with the lever half up. (pre start checks!)
I like the type. Good looking, spacious cabin - over 5 feet wide, relatively fast (100 mph cruise at 11 gph) quiet, stable and can be trimmed to fly 'hands & feet off' ... three seats, a 60- to 100lb, 7 cu ft dedicated luggage locker ... autorotates almost as good as the old Jetbanger, and especially safe. There has never been a fatality in the UK on the type in over 45 years of operation. Due to the large keel surface area, I've landed the Shark safely on two occasions following T/R failure where the left hand control cable was snipped by the up going T/R blade. And once when the T/R drive shaft sheared. BUT I've never had a mechanical engine failure in some 6000 type hours. (14,650 in total rotary) One might be forgiven for asking why any one buys anything else! (only half-joking) And some of you will know, the type is near aerobatic!
I'm happy to answer any specific questions by PM, but the real answer is to make a good type experienced engineer and ditto a FI your new best friends.
Happy and safe flying to all Enstrom pilots on here. Sincerely. Dennis Kenyon.