Home 2024 Forums Opening Section Operational Issues C340A RAM VI – LOP w GAMI

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      HAs anybody been running LOP on their 340 ?
      If so what are the results ?


        Richard, I have been running LOP on my 340 for 10 years and 1300 hours. I have Insight G3 engine monitors to keep tabs on the engine parameters (before that Insight 610s). I normally use 34″ and 2350 RPM and burn 15.2 to 15.8 GPH per side depending on altitude and OAT and get 200 to 204 KTAS from FL210 and higher. If the OAT is high like ISA +15 or higher, I need to use 2450 to 2550 RPM in order to get enough mass airflow to keep the turbos from losing MP when LOP when above FL220. I have AA intercoolers and develop around 70% power with the above settings. My CHTs run from 315 to 375 dF with the EGTs 1610 to 1550 dF. My EGTs peak from 1670 to 1590 dF.

        If the OAT is too high, I cannot keep it LOP above FL230 without a lot of RPM and higher CHTs. So if you see the OAT is above ISA+10 in the winds aloft forecast, then flightplan for FL210.

        When I descend, I leave the throttles and mixture where they were in cruise until pattern altitude. I usually start down about 100 miles out unless I have a huge tailwind as you want the cabin to come down about 500 feet per minute which can be a limiting factor. If you start down too late, then you will need to reduce the throttle which will make the cabin pressure very hard to control as the cabin pressure controller needs boost to maintain cabin pressure. Don’t forget, the boost for the cabin pressure comes from through the sonic venturi which limits the amount of boost that can get through the venturi hole. Sometimes you have to pressure the ATC controller to let you down that far out, but you need to be firm on the clearance as your’s and your passenger’s ears don’t like rapid changes.

        LOP flying takes some continued effort to scan the instruments and get the fuel flows right. The 340 like all twins have a lot of free play in the throttle and mixture controls. To counteract these tendencies, you need to learn how your particular place reacts to mixture control movements. Sometime you have to move the mixture three or four click toward lean and wait a minute or two to see if the fuel flow drops as it is not instant gratification when leaning.

        Sometimes when we are flying back west from the east coast, we will fly below 1,000 above ground level for hours to stay out of the wind. I still run it LOP even way down low, but you need more fuel flow like 16.5 GPH at 1,000 feet and 182 KTAS. Of course, we have two terrain warning systems in the plane along with ADS-B for some traffic, and you get to see a lot of the countryside and oil derricks and cows out west.

        With $7.00 gas, LOP makes more sense. Actually we paid $8.80 a gallon in Prudhoe Bay, Alaska this summer.

        Good flying.


          I did have GAMI’s on my Twin Comanche but never could get it to run smoothly on LOP.
          Any other people have experience for LOP ?


          I concur with Dick’s posting on power settings. I see the same CHT’s
          and EGT’s…… I have fine wire plugs, GAMI’s and a JPI digital engine monitor.

          LOP needs constant vigilance as fuel flows tend to creep over time and need
          fairly frequent readjustment. The benefit is cooler CHT’s, fuel burn and range.
          (perfect timing, solid ignition system and great baffling needed). Do not attempt
          without the proper equipment and training as you could fry an engine
          in a very short period of time. Once mastered LOP offers great benefits.

          The only performance feature I use in addition is when LOP to reduce
          power levels on descent instead of pulling back on Manifold to keep speeds
          below 200kts IAS or to reduce to Va speed…..simply reduce RPM….which reduces
          total HP output and slows you down without adjusting other settings.
          I generally don’t have any problem with pressurization control in descent.

          If you want to know all there is to know about LOP I’d suggest taking the advanced
          Pilot course offered by the GAMI folks…well worth the time and can be completed

          Safe flying

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