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jlunseth last won the day on July 6 2015

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About jlunseth

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    M20K 231

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  1. jlunseth

    LOP MP at high altitude

    First, on the JPI displayed horsepower, Paul is absolutely right. It is important to understand that the JPI does not measure horsepower, it calculates horsepower. In other words it is just an algorithm, and if the constants are not set correctly, then the reading will be wrong. JPI does not publish the algorithm, but from long use of my JPI 930 it appears to work the same way we pilots would manually calculate HP. MP and RPM drive HP when ROP, and fuel flow when LOP. The important point from that is that if your MP was 30” and the JPI was saying 100% HP, then the JPI was just wrong. The other issue though is the MPs you are reporting. Either your MP is not being read correctly or you still have a problem with your turbo/induction system. You should be able to make 36” on takeoff, actually you should be able to make quite a bit more than that, but you don’t want to overboost the engine. The rest of the throttle stem is for keeping power up (by the pilot adjusting the red knob) on your way to the flight levels. If I recall correctly you have the intercooler, but the GB engine and no Merlyn. I would expect your critical altitude to top out right about where you are reporting it, somewhere in the 17k range. The nonintercooled engine is about 15k, you would get a little more, the Merlyn would give you quite a bit more ) it allows the wastegate to fully close).
  2. jlunseth

    231 cowl flaps

    Couldn't agree more. The OP commented that he "leaned the mixture" and that caused the CHT to climb more. I am suspicious that, as Paul said, the fuel flow is set up wrong, or that the OP was already flying at a power setting and fuel flow that was not good for the engine, and then leaned it more making it hotter. It could be a cooling issue, yes, but it could also be an engine management issue, running a turbo at a cruise power setting with the mixture leaned to right around peak or 50 dF ROP as some of the POH settings recommend. That would sure do it.
  3. jlunseth

    231 cowl flaps

    The simple answer is no, opening the cowl flaps to help cool the engine does not hurt the engine. It may reduce your airspeed a little. But that’s what the cowl flaps are for. Higher CHT’s can be any number of factors. Whether the cylinders are getting properly cooled is one. What mixture and power setting you are running the engine at is another? There is a half open setting on the 231 that works pretty well at cruise, you only lose a couple of knots. I have my A & P adjust the cowl flaps to trail (stay slightly open) during the summer, and to fully close during the winter. What was your MP, RPM and fuel flow?
  4. I just had occasion to fly with a local instructor to get instrument current after winter. I wind up doing this (fly with a local instructor) about once a year. Every single time they nudge me to reduce power to 25 squared. I fly a turbo, we are never “squared up.” Its just such dogma they have to say it. As I understand it, the formula worked well to give cadet pilots when they were learning to fly radial combat aircraft. That was a long time ago, but not what we do today.
  5. jlunseth

    Summmer Leaning on Approach

    Me too. Now, the REILs may not fare well, but that is their problem, I’m landing.
  6. jlunseth

    Continental Fuel System Issues

    I haven’t looked at the fuel system diagram in awhile, but I seem to remember some check valves. Is it possible that there is a check valve to prevent back flow to/through the electric pump, and the check valve was somehow disrupted when that pump was installed? Just a thought. In other words is it possible the flow from the mechanical pump is there, it is just getting diverted to fill empty parts of the system?
  7. jlunseth

    Engine quit on takeoff roll

    No, the electric pump should be off during the takeoff. I have a line in my checklist to make sure it is. I have not tried it, but likely it would make the mixture very rich. The OPs problem looks like a fuel starvation event, whatever the cause was. Possible something went in the turbo to drop the MP, but it looks more like the engine was dying and therefore no exhaust to operate the turbo.
  8. jlunseth

    Engine quit on takeoff roll

    Leakage through the cap is an issue. The cap sits in a well so that when installed it is flush with the wing surface. Water collects in the well when it rains, just looking for a chance to get into the tank. If one of the O-rings is bad, that’s all it takes. But there are lots of other possibilities. Failing fuel pump? Did you switch tanks right before takeoffs and perhaps not get the switch fully into a detent position? Failure in the spider? Failure of the throttle linkage?
  9. jlunseth

    LOP MP at high altitude

    There is a major difference between induction failure and exhaust failure. Induction air is maybe 250 dF, and that would be high. Exhaust temp is approx. 1600 dF or more, its a flamethrower. You are very lucky to have survived.
  10. jlunseth

    fuel divider problem? (spider)

    Don makes a really good point about swapped injectors. They are supposed to be tagged so they won’t be swapped, but the tags can come off somewhere along the way. All it takes is a mechanic replacing the injectors who does not understand what GAMIs are, or just forgets the way the cylinders are numbered, different for Lycs than Contis.
  11. jlunseth

    Speed on final J model

    I have a little time in a J, about 20 hours, and alot of time in the 231. The K is heavier and speeds are a little faster, not much, but about 5 knots. I did notice that the J liked to float. But in my opinion, final approach and landing speed in the J and K are a function of where you live and what weather conditions you face. In gusty crosswind conditions you need a little more speed to get the necessary rudder authority. In addition, there is almost always a headwind component, which slows the ground speed (not the airspeed). I have made an awful lot of landings at 85 kts. in the 231. I like to land it at 75, or even at 70, but most of the time in the midwest that just won’t work. It can be a major mistake to come in on short final at slow speeds like that and then get hit by gusts right above the runway that exceed your elevator authority, or even get hit with a tailwind just above the ground. I have landed in sunny day windy conditions on rural airstrips with winds gusting in the 20s and varying in direction by 120 degrees. So I agree with both of you. I would prefer to land the J at 70, better control over descent rate and not so much float, and if the winds are light or stable I would do it that way, but alot of the time where I live I would use a higher landing speed.
  12. jlunseth

    LED lighting Poll

    I have both. I have LED nav and tailight and they are STCd or PMAd, I don’t remember which. I have an LED landing light and as I recall that was just a drop in replacement signed off by the A&P. No one has ever said boo about either of them.
  13. jlunseth

    Oxygen ... need a little help

    Well, be aware of a couple of things about pure O2. It is not necessary to have a spark to ignite oil in the presence of pure O2. The oil and pure O2 will spontaneously combust, and when I say “will” I mean “will,” it is not a “maybe.” In technical scuba, where divers are using O2 air mixes that are over 40% O2, all of the regulators must be specially cleaned to get rid of any petroleum based lubricants, even the thin layer of grease on O-rings. There cannot be any petroleum - no quantity at all - in the system. Even things like lipstick or lip balm are an issue in the presence of pure O2. There have been instances where divers were injured because of O2/petroleum combustion. This is the reason why O2 tanks have green bands or green paint, it signifies that the tank and regulator are safe for use with high O2 mixes, including pure O2. When these tanks and regulators are serviced, they must be serviced using non-petroleum parts and lubricants, we use special greases for the O-rings that do not contain petroleum. So a few things. First, if and when you buy a regulator for your O2 bottle, it must be a regulator certified for use with O2. You can’t just go buy a regulator somewhere and stick it on your tank, ordinary regulators meant for air are all contaminated with petroleum based lubricants. Second, it is not a very good idea to have your tank rolling around loose in a cargo compartment with some quarts of oil. Obviously, if the oil bottle is sealed, there is no way the oil and O2 can mix, but if there is a leak in the oil bottle, or a bottle has been opened and partially used, there is enough for combustion, and all it would take would be a leak in the regulator to cause a fire, there would not need to be any spark or other ignition source. Third, the built in systems all have a shut off valve at the pilot station. It is not a good idea to have the shut off valve completely inaccessible because there is no ability to cut the O2 flow off in the event a fire does occur. It is not a very good idea to have a tank with a regulator on it lying in the back of the luggage compartment, and then start loading luggage in on the tank. The regulators are durable, but it is possible to break one, it is rare but does happen on dive boats that a tank falls over, the regulator strikes something hard, and cracks. I would not want a tank under luggage in the cargo compartment, with the movement of the luggage able to turn the valve on or off, or possibly damage the regulator.
  14. I use that calculation when flight planning to cross Lake Michigan. I try cross at the narrowest part, which from memory is 44 miles, and I try to get to at least 12k, not always possible because of weather, etc. but that is what I try for. Also really need to be aware of the wind. I have made several trips across where west to east we can coast to the eastern shore as soon as we break the western shore, but coming back east to west I will go around Chicago. On a couple of occasions I have had to negotiate with ATC that sets up a course where a west to east perpendicular crossing can be done, particularly when I have human treasure on board. Its just a planning thing to think about, eliminate a risk if you can.
  15. Altitude is a real treasure. Better to have lots of altitude and a need to find a way to lose it, than not having enough, which you can’t fix. For quick math (that’s all the time you have), I use a two mulitplier. The glide ratio at best glide is 12.7:1, which is a little over 2 nm per 1,000 feet AGL. At 19,000, with most of the airports in the midwest at around 1,000 MSL, that’s 36 miles. In Minn., where I fly quite a bit, its rare to find a place where the airports are more than 20 miles apart, so there are many options. Now Foreflight draws a constantly updated “glide circle,” flatter to windward than to leeward, have not needed to use it in a real situation though. The only time I can think of when altitude is not an advantage would be a fire that you are unable to put out, very rare but possible. I think I would choose to test Vd on that one. Knock on wood.