Hi Ric, The running rough thankfully disappeared once I had the carbs entrails thoroughly cleaned. Regarding the engine tbo, I am clearly pushing my luck. I am mostly looking forward to pure soaring flights with minimum engine time (particularly when winter's over in 5 months).
Regards Jarek On Sat, 9 Nov 2019 at 13:40, Ric Sutton <[email protected]> wrote: > Hi jarek > > I don’t want to be alarmist but i think the tbo on our engines is 1000 > hrs. I recall you had trouble with yours running rough at some stage did > you ever find the cause of that? > > > > *From:* [email protected] [mailto:[email protected]] *On > Behalf Of *Nigel Baker > *Sent:* Friday, 8 November 2019 8:57 AM > *To:* [email protected] > *Subject:* RE: [DOG mailing list] H36 top speed > > > > The guy who will remain nameless who did the initial inspection of VH GNW > to get an OZ C of A told me about the holes that had been cut as you > described. > > A the time I was in contact with Diamond changing the rod ends over in our > 3 Dimona’s and that’s how it came up in conversation. I was surprised he > didn’t seemed concerned. Those roving’s as you know are critical in the > connection of the undercarriage to the fuse. He later lost some of his > ratings dud to a dodgy major repair and left gliding shortly later. Haven’t > heard of him for well over a decade. So yes the holes were not cut ion OZ > but came from the Thai Airforce like that. Their maintenance as you know > was beyond awful. > > Nige. > > > > *From:* [email protected] <[email protected]> *On > Behalf Of *Ian Williams > *Sent:* Friday, November 8, 2019 7:40 AM > *To:* [email protected] > *Subject:* RE: [DOG mailing list] H36 top speed > > > > Hi Nigel, > > > > A great reply. I read all your responses at least 10 times to absorb > what you describe. I am still a learner compared with you , Rob and > others in Oz. The thing that has pushed me into working on VH-GNW and WVW > really has been the experience with both the repair and flying of our > Dimona ZK-GCB. I recall you mentioned some years ago comparing the > Dimona with a Grob 109 You are right … the little Dimona has exceeded > my expectations by 100%. Not bad considering the design is now 40 years > old. > > > > Relating to fuel … > > A couple of Mths ago a very good friend asked me to ferry his Fisher Tiger > Moth (About a 0.8 scale) from one airfield to another … about 15 min flying > time. The engine is a Walter Micron Mk3 (85 hp) We topped up the tank > with fuel from a plastic container (Mogas) Well, I set off and all was > good (or seemed OK) though the RPM was a little lower than I expected. > Leaving the circuit and heading South, everything turned to custard. > Smoke, vibration and no power … Shit!! So a controlled descent into > the Auckland gliding club strip which was fortunately strategically > placed. A nice little hole in the rear piston. We have it back together > and was able to continue the ferry flight (but was a mission to repair and > another story) The thing here is the fuel we put in had been stored in > a plastic container for a longish period of time. So had gone off big > time. Low octane causing bad preignition. So beware of storing your > fuel in plastic containers. > > > > The 500 hr inspection relates to all the fuel lines forward of the > firewall if I have read the MM correctly > > > > We don’t have a technical engineering panel here in NZ so all work has to > comply with the factory MM or a major repair factory approved. (though I > am sure any GFA engineering decision would be accepted over here) . > fortunately I do have associates who have had many years composite > aircraft experience so am fortunate there. We are still discussing the > repair to GNW . Our current thinking is to utilize the fittings from > WVW. We are currently cracking all the joins of the centre section of WVW > internal panels so will see your repair. We have the detailed drawings > of that area which show the Rovings and how far they extend into the > structure. With GNW, someone (suspect the Thais) have cut(100mm * 80mm > approx.) holes into the outside skin in front and behind the rod end holes > on both sides. .. cutting through rovings laid on the skin. The holes > were covered with aluminium plates attached by rivnuts drilled into > rovings … really quite ugly. I am sure that was not done in Australia. > > > > I will keep in contact with you Nigel regarding the repair to GNW as we > progress. > > > > Best regards > > Ian W. > > > > > > *From:* [email protected] *On Behalf Of *Nigel Baker > *Sent:* Friday, 8 November 2019 2:30 a.m. > *To:* [email protected] > *Subject:* RE: [DOG mailing list] H36 top speed > > > > I thought I had addressed your concerns in my mail. > > Dealing with the fuel hoses etc. should be easy. > > The manual gives a life of 5 years for the fuel hoses in the H36. > > Anyone in OZ paying attention to the GFA engineering panel advice would > have used 1 of 2 types of hoses preferred and both of which are OK for > avgas and low lead alcohol. > > If using hose supply from either Diamond or Limbach then the fuel is > appropriately approved for the fuel types. > > > > The electric fuel pump also has a life. The previous pump and the > replacement both are ok for said fuel types as I understand. > > The old mechanical fuel pump rubber parts were OK for said fuel types. The > new replacement pump as the original type is out of production surprise > surprise and the new Italian replacement is also OK. > > The Carb diaphragm and parts were and still are OK with these fuel types. > So assuming the manual has been followed then all the relative items should > have been dealt with but it should all be easily checked from the aircraft > maintenance log and in my case most certainly so. > > It is all clearly listed in my log book otherwise I wouldn’t know where I > was from one year to the next. > > I am not suggesting digressing from the certification of the aircraft at > all. If all that is correct then my only remaining concern is those like my > aircraft that still have the original FRP tank and not the alloy > replacement as per the SB. So until 3000 hours in accordance with the SB I > will happily check the tank each annual for degradation but so far so good. > > > > I warned about dud fuel and the likelihood of detonation in my post. This > subject has been dealt with multiple times on the DOG list and I would hope > all members are across that problem. The H36 is a pretty quiet aircraft and > it amazes me how anyone can miss the sound when it is all wrong. But then > again Rob and I a couple of years ago had the pleasure of inspecting the > cylinders and heads from an L2400 fitted to a Typhoon which had a history > of being flown outside the top CHT range. The detonation had destroyed the > heads and pistons. The CHT got so high the barrel tops softened resulting > in them swelling out under combustion pressure to the extent that the > cylinders and heads could not be separated. > > We put the cause down to excessive CHT due to the history we knew. > Strangely when asking the pilots about the pinging sound resulted in blank > looks. Maybe they were not aware of the symptoms and sound. In any event we > have covered fuel quality at length in the past on this mailing list. > > > > As I pointed out the rules we operate under here down under are very > different and local requirements and governess must be followed. > > > > I have attached some pics of the holes cut for the rod end bearing > replacement. These were cut with the aid of drawings from diamond. The > large ones to the side of the control stick I reinforced with a cast ring > made of glass roving’s on the underside of the seat panel. It was not > required by the drawings but seemed like a good move. > > The small hole at the bottom of the front seat panel section was to be > able to get an in hex drive into the SHCS that holds the rear rod end in > place. > > The hole in the floor in front of the seat section is the front rod end > mounting. It is better to start further forward and work backward toward > the seat to avoid inadvertently damaging the roving’s. > > > > The seat assembly and Centre console form part of the fuselage structure. > Especially over the tunnel for the undercarriage bow where there are > complex being moments. > > Thus repair is really only practically achieved from the outside not > inside. > > It is not a difficult repair but it is complex and done in stages. > > VH WVW had this repair done to it after a really really really heavy > ground strike/heavy landing incident. > > The steel tube that spans between the front and rear rod ends was replaced > and laced back into place with roving’s as original and then the rest of > the structure laid up from there working outwards. > > Like I said things are different here so no need for a factory approved > repair scheme. In fact some years ago Alexander Sleicher released an SB > that clearly stated that any fiber repair could be carried out following > the repair principles defined in the Maint Manual “including propellers” as > long as the person is approved for the task in the country of operation. > > That is me and quite a few others who have the training and experience to > do the damage and repair assessment as well as being able to carry out said > repair which usually includes jigs, molds. Vacuuming etc. not simple stuff. > > > > Cheers. > > Nige. > > > > > > > > > > > > > > *From:* [email protected] <[email protected]> *On > Behalf Of *Michael Stockhill > *Sent:* Thursday, November 7, 2019 10:22 PM > *To:* [email protected] > *Subject:* Re: [DOG mailing list] H36 top speed > > > > My concern regarding use of alcohol blend fuel is this: > > > > While the current manufactured Limbach and Rotax may be certified for use > of such fuels, is there any assurance that soft parts such as hoses and > seals used and still existing in older aircraft and engines fabricated > before these fuels existed can tolerate alcohol without degradation? > > > > In addition, in a previous life I investigated a Beech Bonanza accident > where the owner was using auto fuel, notwithstanding the fact that its > Continental engine was not one qualified for a supplemental type > certificate (STC). Removing one spark plug and seeing the piston's bead > blasted appearance was all that was necessary. He had gotten away with his > charade for quite a while, until he onloaded some fuel that was of lower > octane than advertised. Sourcing auto fuel lends a bit of trepidation to > its use in airplanes. > > > > M > > > > On Thu, Nov 7, 2019, 12:10 AM Nigel Baker <[email protected]> > wrote: > > Hi Jarek Ian and all. > > I have experienced this pitch problem once before on an IS 28 M2 (worst > aircraft I have ever flown) and while I knew the answer I didn’t tell the > owner as I considered him a loose cannon on maintenance. He wrote the > aircraft off during landing which was pretty predictable given what I had > noted in his flying and thus I was never asked to fix his problem. > > > > I have been looking for the appropriate data which I have somewhere but > can’t put my hands on for the dimension of the pitch change step on the > pitch setting nut’ > > I have found data for the 2 pitch angles between climb and cruise but not > the step dimension. > > The nut I refer to is the round nut which is fitted to the central pitch > drive shaft which is positioned beneath the alloy channel with the nylock > nut on top to secure it all. > > That nut has a step in it that the slide plate engages with the nut when > de pitched in flight for pitch change. > > To understand it you need to remove the spinner and action the blades by > twisting at the root to move pitch position then move the slide out from > Centre and release the blades to lock back on the nut. That is the cruise > position. A small twist of the blade allows the slide to return under its > spring force towards Centre and on releasing the blades it is locked in > climb pitch. > > Centrifugal force is what courses the slide to move out from Centre hence > the need to change to cruise at around 2200 and climb near idle. > > I hope you have grasped my explanation but toying with it the best way to > work out how the function works. > > The nut sets the climb pitch position so yes 3000 static is good. > > Bring the RPM back to cruise pitch change RPM and do the change then open > the throttle again. > > If you get a static drop of 200 to 250RPM then the prop is fine. > > If it is greater and the RPM Is less than 2600-2700 RPM then I suspect the > wrong nut was installed at your recent factory service. > > To check this using the angle data which is listed in the prop manual > requires accurate angle measurement so best done by a competent propeller > ground engineer. > > > > I am not near my aircraft which is over 200ks from me. However if Ian > Williams or someone else is in a position they could give us a reference to > check to. > > To do so remove the spinner and set the prop in the cruise position. > > Now using feeler gauges the distance between the climb position step and > the pitch select slide. > > > > This propeller is used on many aircraft types and thus settings for fine > pitch and cruise vary a lot. The change in amount of pitch is controlled by > the length of the step in the nut. > > The Longeazy is a good example. The RPM change from climb the cruise is > significant. Slippery in cruise hence the big pitch change. > > > > The ASK14 has a Hirth 4 cylinder 2 stroke engine and a 2 position Hoffman > prop. Same assembly but without the slide. I know a couple of this type > have had the nut replaced and the slide assembly added so it has 3 > positions like ours. > > I also know someone who has made his own nut with 2 steps so he has 4 > pitch positions. > > I am not suggesting any of this is wise or legal but telling you this so > the versatility of the unit is understood. > > > > If I am correct about my best guess of the problem from previous > experience then Hoffman need to fix their mistake and fit the correct nut. > > If you are having trouble reading and understanding my descriptions then > consider how hard it has been for me to write this. I keep reviewing it to > make sure it makes sense and is understandable. I have likely failed. Sorry > but the best I can manage. > > > > The Limbach and Rotax engines are permitted to run on alcohol blends and > is becoming the norm in that class of engine. > > In the Limbach engine the rubber components being the factory fitted hoses > on the engine, the Carb and fuel pump diaphragms and seals etc. are rated > for alcohol blends. > > The engine is certified for alcohol blends. > > Around the world alcohol blends are becoming the norm for mogas. In > Australia there are 2 states where the use of alcohol is mandated in mogas > so you really can’t avoid it. > > > > Peter Limbach told me the reason the Limbach is certified for Avgas as > well as 98 unleaded is because of certification requirements and market > acceptance rather than by simple choice. > > He prefers unleaded. > > Except for lead, avgas is the purist fuel on the market. Mogas specs > change with the season keeping your car running smoothly so it is far from > pure. > > Discussing issues I have found on top overhauls, full overhauls and prop > strike bulk strips on engines running on avgas (Including the L2400 DFI > 100HP liquid cooled engine prop strike) he agreed with my views and said > yes that’s why we prefer you run on unleaded. > > The lead fouls spark plugs yes, but even worse it fouls valves especially > the exhaust and cakes thick on the combustion chamber and piston crown. > This build up causes run on at shutdown/hot spots for ignition etc. It also > fouls the piston ring grooves and can lock the rings as I have seen happen > before. I have also experienced exhaust valve failure caused by it leaking > due the build of that horrible yellow cake. > > > > Having said all that there are some other considerations to be respected. > > I almost exclusively use unleaded. Some times I am not able when touring > and the mogas point in town is a long way from the airfield so I use the > on field FBO reluctantly. I am always wary of the fuel octane with mogas. > The fuel companies mess with the formulae a lot to meet the 98RON. This > results in volatiles that will at times rapidly evaporate out and reduce > the RON significantly. So always be aware of the risk of detonation. It may > come from the pump already degraded or often degraded while sitting in the > tank if the aircraft sits idle for some time. > > Avgas can also degrade in the tank over time but the time factor is > significantly longer and thus not usually a problem. > > > > While our engine is rated for alcohol blends you must also consider the > suitability of hoses and boost pump used in the airframe for alcohol blends. > > That is actually easily achieved in our case. The let down is the fuel > tank if it is composite rather than alloy. There is a question mark on the > resin used in the tank manufacture. I check the tank each year as per the > SB and have not ever detected any degradation. However someone in a > different country could well have a different result with their local fuel > supply. So due diligence is required to meet the requirements of your local > aviation authority, tank inspection, and checks on the other fuel carrying > items in the airframe for suitability. > > All issues must be considered carefully. Meanwhile I don’t use avgas and > advise others in OZ to do same but our rules are set by our sporting body > the GFA not the government body. We are very different and what we can do > here often is not possible in other countries. > > > > Hope my ramblings are of help. > > Cheers. > > Nige. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > *From:* [email protected] <[email protected]> *On > Behalf Of *Ian Williams > *Sent:* Wednesday, November 6, 2019 7:42 PM > *To:* [email protected] > *Subject:* Re: [DOG mailing list] H36 top speed > > > > The RPM’s and speeds are what suits us. There are only 2 Dimona’s in > New Zealand .. some distance from each other. > > So it would be good to get data from other Dimona operators. > > IW > > Sent from my iPhone > > > On 6/11/2019, at 9:38 PM, Ian Williams <[email protected]> wrote: > > Yes … an L2000 Limbach and an HOV62 prop. > > What is your static full throttle RPM on the ground ? > > > > *From:* [email protected] *On Behalf Of *Jarek Steliga > *Sent:* Wednesday, 6 November 2019 9:14 p.m. > *To:* Laurie Hoffman via dog <[email protected]> > *Subject:* Re: [DOG mailing list] H36 top speed > > > > Hello Ian Williams, > > > > I am really worried after reading your reply. Are we talking about H36 > with Limbach 80PS and Hoffmann HO V62 propeller? If so, what could be > the reason for the serious underperformance of my power plant? > > > > > > Regards > > Jarek > > > > > > > > On Wed, 6 Nov 2019 at 09:05, Jarek Steliga <[email protected]> wrote: > > Hi Ric, > > > > 1600 hrs / 12 atm pretty consistent on all cylinders > > > > Regards > > Jarek > > > > > > > > On Tue, 5 Nov 2019 at 12:46, Ric Sutton <[email protected]> wrote: > > Hi Jarek how many hours do you have on your engine/ what are the > compressions like? > > > > *From:* [email protected] [mailto:[email protected]] *On > Behalf Of *Jarek Steliga > *Sent:* Monday, 4 November 2019 5:06 AM > *To:* [email protected] > *Subject:* [DOG mailing list] H36 top speed > > > > > > > > Hello, > > > > I noticed that at level flight with the prop at cruise angle I can hardly > reach the air speed of 150 km/h at RPM 2500 (full throttle). Is this > something to worry about? Should not the top speed be around 190 km/h at > RPM 3000? > > > > With the prop at "start" position the full throttle revs are 3000. > > > > Any comments please? > > > > Regards > > Jarek > > > > > >
