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Schweizer & Enstrom engines

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I would appreciate information from mechanics, pilots, CFIs or anyone familiar with these engines mentioned below.



The Enstrom uses a Lycoming HIO 360 F1AD engine that is turbocharged and runs at 3050 RPM to produce 225 HP.

The Hughes / Schweizer 300 uses the Lycoming HIO 360 D1A  and runs at 3200 RPM to produce 190 HP. Both engines have TBO at 1500 hrs. The question is if used in the exact same flying situation ,which engine is more likely to make its TBO or go past it? Which engine is under more stress, or are they about equal? The Enstrom is running at lower RPM., but runs at a hotter temp because of  the turbocharger. On the other hand the Hughes 300 is running at a higher RPM., but should  run at a lower temp., not having

hot air forced into it from a turbocharger.


The Enstroms engine is supposedly beefed up to handle the turbo, what area did Lycoming beef it up?


Is the Hughes 300 engine beefed up in any way for use in a helicopter?


I may have a lot of information wrong, so please correct me if so. This is something I am curious  about and would appreciate  any information.

























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The "H" in HIO-360 stands for "helicopter horizontal", so from that standpoint, both the D1A and the F1A are (re)designed for helicopter use.


From what I've seen, the Schweizer 300C is more likely to make TBO than the Enstrom. Part of the reason is that although the D1A is rated at 3200 RPM, Schweizer recommends 3100 RPM as the normal operating speed. The bigger reason is that the Enstrom tends to burn it's exhaust valves pretty easily - you really have to watch the EGT and manifold pressure. The Schweizer has MP limits as well, but if you exceed them, the damage is not as quick or severe (although you will pay the piper eventually).

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When I went to the Enstrom maintenance school, we were told that the HIO-360-F1AD was a big improvement over it's predecessor, the HIO-360-E1AD utilized in the earlier "C" model Enstroms. The newer model engine has a stronger crankshaft and camshaft, enabling it to handle the higher RPM's, loads and stresses which allow the engine to make it to the recommended 1500 hour TBO. Lycoming did not initially incorporate the turbocharger on the earlier engine, whereas Enstrom installed it on the engine. Latter on, Enstrom asked Lycoming to desgn a stronger version of this engine and to also incorporated the turbocharger into the factory design. This is how the engine evolved into the F1AD model series.


The owner of an F-28F attended the same factory maintenance class that I was in, and his engine had more than 1500 hours TT. We were all told by the Instructor that he could operate it beyond the reccommended TBO if all the vital signs, (i.e. compressions, metal in the oil, etc.), were with in the established tolerences; since the "1500" hour TBO is a recommedation and not a requirement.


I have also talked with a few Enstrom maintenance shops and police departments that have a lot of experience operating/maintaining this engine and I have been consistently told that the engine makes it to TBO without a problem. The critical key to the engine's longevity is proper operation and engine cool-down at the end of every flight.


I do not know much about the DIA's used in the Schweizer's other than it is also a stronger built version of it's predecessor used in earlier Hughes 269A models.

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Ga Chopper excellent information, its good to know that the newest engine in the Enstroms is making its 1500 hr TBO recommendations and also in some machines going past the recommended 1500 hr. TBO. I also agree that proper cool down at the end of the flight is essential to long engine life.


I am not very familiar yet, with  a fuel flow & EGT gauge, but doesn’t seem that it would be very difficult to control.  I will find out in a few more weeks when I get a chance to fly it. I think its probably one of  those tasks that become second nature with time. Is that the way it is with you and your machine? Also I thought there would be a fairly good  manifold pressure reserve in the Enstrom under most conditions, what is your observation?


Helidoc or any one with experience in the Enstrom turbocharged ships what is your opinion on  controlling EGT/ fuel flow gauge? Say from a hover to cruising altitude?





Thanks in advance



P.S.       Have you taken the CFI check ride yet?

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The turbo-charger's EGT and fuel flow are easy to manage with the mixture control, plus it will become second nature as you have stated. After the engine is started, I initially set the mixture to a "ball park" setting and then I fine tune the mixture using the EGT and fuel flow in the hover. Hovering is where you will generally encouter the highest EGT and manifold pressure. After transitioning thru ETL, I set the manifold pressure to about 30" for the climb with two people onboard and the EGT cools down slightly. In cruise flight, I set the manifold pressure anywhere from 25" to 30" depending on how fast I want to cruise and then I might fine tune the mixture again but not always. The maximum manifold pressure for my engine is 36.5" whereas I think it is 38.5" for the F1AD, so you do have plenty of reserve power in all phases of flight for any of the turbocharged engines used in Enstroms. It seems if you initally set the EGT in hover, it is usually fine for all other phases of flight since you are using less power.


The Enstrom POH states the maximum EGT for flight is 1650 degrees F, this limitation is primarily for the turbo-charger. I think that is too high of a temperature to lean the mixture to, since it can easliy cause a cooked turbo-charger or burned exhaust valves. I never exceed 1550 during winter flying or 1450 in the summer since it seems to also keeps the cylinder head temperatures and oil temperature in the "green".


I have a GEM, (Graphic Engine Monitor), installed in my F-28C-2 and highly recommend one for everyone who owns an Enstrom. It monitors each of the four cylinder's EGT, cylinder head temperatures and turbo-charger EGT. This gives you a total overall picture of engine's operation and will show the first indication of an impending problem. It will allow you or your mechanic to troubleshoot for: a fouled or dead spark plug, a plugged fuel injector, proper magneto timing and many other impending failures beginning to occur in any cylinder. I once noticed that one of the cylinder's EGT suddenly increased during cruise flight and quickly found it was caused by an intake leak. I would have not known about this if it were not for the GEM and this condition would have eventually caused a burned exhaust valve or cylinder damage.


So far I have 1200 hours TT on the original engine and airframe. The cylinders were all top overhauled at a 1000 hours mainly due do the age of the engine, which is 25 years old. I think the main reason that this engine has been doing well so far is because of the GEM, it allows you to effectively operate/monitor the MP, EGT's and CHT's. Plus a proper engine cool down ensures longer life of the cylinders and turbo-charger.


If the weather holds up, I will take the CFI check-ride next week.


Good luck with your Enstrom!

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I would wecome your opinion on cooling down my non turbo 28A. I have a EI multicylinder monitor and I generally approach my LZ with no power on. The hottest head temp is often below 350f when I land which is what it says in the book for shut down. Would you think it wise to cool more or is it OK shut down straight away?


I generally cool till number 4 hits 320f.



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I agree with your procedure and that will help ensure that you do not end up with a "stuck open" exhaust valve due to an inadequate cool-down.  A stuck open exhaust valve can cause piston/cylinder damage as well as cam lobe damage, (read very expensive overhaul).


A good cool-down will also help to prevent "thermal shock" to the aluminum cylinder heads and help eliminate cracks from developing around the boss for exhaust valve.


I cool the engine down as you do for the CHT's plus an addtional 2 minutes for the turbo-charger. This is to prevent oil coking which will damage/seize the bearings in the turbo-charger.

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