Scottknoll Posted November 30, 2022 Report Share Posted November 30, 2022 1 hour ago, midlifeflyer said: You're expecting people to read the Systems section of the POH to understand the aircraft systems? I’ve been called an evil CFI in the past. Even the AFM leaves a lot to be desired. Sometimes the Mx Manual helps, but not always. 1 Quote Link to comment Share on other sites More sharing options...
Scottknoll Posted November 30, 2022 Report Share Posted November 30, 2022 Interestingly, when I follow the Mooney hot start procedure (Full throttle, mixture cutoff, boost pump on then off) I get fuel departing the engine compartment after 8-10 seconds of low boost pump. Continental says Mixture cutoff and Throttle IDLE and boost pump per AFM. In this condition, it takes a little longer (20 seconds). But I still get fuel under the engine. Continental manual says the fuel manifold valve positively stops fuel under 1.0 psi. I must be getting over 1.0 psi even with the boost pump on and throttle idle / mixture cutoff. Not sure if this is normal in the Ovation set up or not. I’ve found that I can complete the hot start procedure per Continental’s guidance and just limit the boost pump to about 10 seconds to prevent fuel puddling. Quote Link to comment Share on other sites More sharing options...
rbp Posted November 30, 2022 Report Share Posted November 30, 2022 7 hours ago, PMcClure said: As I understand, running the boost pump with mixture off builds pressure which will overcome vapor lock. seems plausible, however "vapor" is compressible, but "liquid" fuel is not, so I'm not quite sure about "build[ing] pressure" to overcome vapor lock. conjecture only, as I'm no expert. but if it works, it works! Quote Link to comment Share on other sites More sharing options...
kortopates Posted December 1, 2022 Report Share Posted December 1, 2022 seems plausible, however "vapor" is compressible, but "liquid" fuel is not, so I'm not quite sure about "build[ing] pressure" to overcome vapor lock. conjecture only, as I'm no expert. but if it works, it works! although it does build pressure, what it’s really doing is recirculating hot fuel back to the wing tank through a return line at the pump and bringing up fresh cool fuel before starting. Only Continentals do this. Sent from my iPhone using Tapatalk 2 Quote Link to comment Share on other sites More sharing options...
Will.iam Posted December 1, 2022 Report Share Posted December 1, 2022 2 hours ago, kortopates said: although it does build pressure, what it’s really doing is recirculating hot fuel back to the wing tank through a return line at the pump and bringing up fresh cool fuel before starting. Only Continentals do this. Sent from my iPhone using Tapatalk Which is why I’m confused he said with mixture at idle cutoff he is still getting fuel dumping overboard. Did i not read that right or is his mixture control not working properly? Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 1, 2022 Report Share Posted December 1, 2022 Just wait a second…. Fuel systems are engine specific…. And manufacturer specific…. And sometimes even airframe specific…. For the Ovation…. 1) Running the pump with the mixture at idle cuts off… recirculates fuel back to the tank from where it came…. 2) There isn’t any pressure building, beyond enough pressure to send it back…. 3) It isn’t pressurizing the fuel to make vapor bubbles disappear/condense… 4) It is using cool fuel from the tank, to cool the lines that are in hot places…. So vapor bubbles, in that section, don’t form… 5) Keep in mind… there is still part of the fuel system that is still hot, and won’t get cooled by this recirc….. 6) You will see the hot start procedure can use a lot of recirc time for cooling…. 7) Heck… we didn’t even get a fuelP gauge to measure if there is even pressure in the system! Soooo…. Preparing for the start is all about… 1) Having cool, vapor free fuel lines…. 2) Filled with cool liquid fuel…. 3) priming with a known amount of fuel 4) The known amount is based on ease of fuel evaporation…. (CHTs, Engine temp, OAT, OilT, all have a hand in this…) 5) Delivered by the fuel pump switch of your choice… (timing is based on FF of the switch selected) 6) The Lo switch is a bit more forgiving than the Hi switch… and adds some precision. 7) Precision is measured in one second intervals… notes… Lycoming engines don’t recirculate fuel… Some Mooneys when recirculating, only send fuel back to one specific tank… (fuel selector switch complexity) We are only a few steps away from having a simple starting system like an automobile…. Find what works… it is very repeatable…. Keep doing it. If it doesn’t work… figure out what is still changing…. Of the O’s engine doesn’t start… it is highly likely to not have enough fuel going to it… It doesn’t flood easily… PP thoughts only, not a CFI… Best regards, -a- 2 Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 1, 2022 Report Share Posted December 1, 2022 That other topic that came up… Fuel puddling under the engine after start… 1) That probably isn’t right… 2) How did you find out? Things to look for… The O has three fuel drains… Which on start-up should remain dry 1) Each fuel pump has a drain… if fuel comes out the drain… it is pump re-seal time…. (Been there done that…) 2) We have a sniffle valve… that is supposed to drain excess fuel from the intake system…. It is a check valve that closes when engine vacuum is developed…. If the sniffle valve is draining fuel from the (known volume) priming…. That sets up a quirky situation… an unknown amount of prime is now leaving the system… Back to the how did you know question?…. 1) When you prime the engine… you have several seconds for the fuel to evaporate… It isn’t prime and start immediately… 2) If you take a few minutes to walk around the plane…to have a look… get back in, and then attempt to start…. This adds another variable 3) The system is open to the atmosphere, time is a real part of the equation… Too quick, not enough fuel can evaporate…. Too slow, some fuel evaporates, and some starts heading for the exit…. Most excess fuel ends up getting drawn back into the intake… It’s probably not normal to have fuel end up on the ground after start… but, I don’t know that….. it’s been prime, wait, start…. Taxi off. I always look back, but a small amount of fuel left behind can’t be seen from the pilot’s seat. I’m looking for the big things at that point. Hangar door closed, car put away…. How I found out my electric pump was leaking… I primed for start… My neighbor waved at me… to tell me something was leaking… a lot! The pump was pulled and sent to get re-sealed… A leaky pump may drip while in the hangar… soooo… if you see a blue spot under the engine on the floor… try to determine which of the three drains is creating it… PP thoughts only, not a mechanic… Best regards, -a- Quote Link to comment Share on other sites More sharing options...
Scottknoll Posted December 1, 2022 Report Share Posted December 1, 2022 I was curious why Mooney and Continental have different hot start procedures. Both call for mixture cutoff (makes sense). But Mooney says Throttle full, and Continental says idle. Then boost pump on (low 15 seconds or high 5 seconds).I knew it was supposed to just circulate fuel, but I was still nervous about flooding. So one day I decided to check. Wasn’t flying that day, but set up and ran the pump both ways (mixture cutoff and throttle full vs idle). That’s when I discovered the difference. Low boost started dripping in 8-10 seconds with full throttle vs 20 seconds with idle throttle.I know I want to pump enough to return vapor to the tanks and fill the lines with cool fuel. That’s why I settled on Continentals procedure (Throttle Idle), and only 10 seconds of pump time.The fuel was coming out of the sniffle valve. Just curious if any other Ovations act like this. But you’re right, no one would know unless you ran the pump long enough and got back out before starting for some reason.In my case, everything else engine wise works as expected and the fuel system was set up my a well known NJ MSC, so I do have faith that it is correct. I’m not sure what the pump output pressures normally are, but it seems like more than 1.0 psi is reaching the fuel manifold valve.Step 5 does say to allow the fuel to drain from the cylinder drains so it sounds like this is normal. Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 1, 2022 Report Share Posted December 1, 2022 The Mooney POH should be a cut and paste version of the Continental operations guide… Continental knows how to start their engines… Mooney knows how to edit for their specific application… Make sure you are getting the info for single engine land plane vs. some other application that the IO550 can also be appropriate for… PP guessing only… Best regards, -a- Quote Link to comment Share on other sites More sharing options...
kortopates Posted December 1, 2022 Report Share Posted December 1, 2022 (edited) 6 hours ago, Scottknoll said: The fuel was coming out of the sniffle valve. Just curious if any other Ovations act like this. But you’re right, no one would know unless you ran the pump long enough and got back out before starting for some reason. In my case, everything else engine wise works as expected and the fuel system was set up my a well known NJ MSC, so I do have faith that it is correct. I’m not sure what the pump output pressures normally are, but it seems like more than 1.0 psi is reaching the fuel manifold valve. This isn't normal; especially with throttle closed . But there is an exception only if the engine driven fuel pump is the latest design. In the latest TCM revision they did open a galley that allows fuel to go forward out the pump to the throttle body and fuel divider at ICO. Prior to this it was impossible and most engines out there still have the older design. even during pump overhaul there is no requirement to bring the pump up to the latest revision in the TCM IPC; you'd pay extra for that. So this exception of the newer pump applies to very few. I have it but still don't see what you state. The fuel divider valve specifies 3.5 PSI to open it it, not one 1 psi. Thus without 3.5+ psi, fuel won't get into the fuel divider/manifold. Anyway, I use this procedure all the time, but because I am an informed (being an IA and a CFI) I only use low boost rather than high boost to minimize fuel getting to the cylinders since I have the new pump design - it seems like common sense to me. But I find vast majority of pilots much prefer the high boost because it's half the time. But when you do your own maintenance it encourages you to be much more conservative about aircraft limitations. For example, I'll never drop my gear at max 140 kts, it got to me under 120 kts; preferably at 110 same as max flap extension speed which I am also more conservative about... Edited December 1, 2022 by kortopates Quote Link to comment Share on other sites More sharing options...
Scottknoll Posted December 2, 2022 Report Share Posted December 2, 2022 Thanks Paul, very helpful. I had no idea there was a new design that would let fuel through in that manner. I was getting the 1 psi from the TCM M-0 manual posted above. Quote Link to comment Share on other sites More sharing options...
larryb Posted December 2, 2022 Report Share Posted December 2, 2022 Low boost, mixture and throttle closed in my 1997 Encore results in around 2.5 GPH shown on my JPI. Since the JPI sensor is between the fuel pump and the fuel divider it would represent actual flow to the cylinders. My engine driven fuel pump has been overhauled in the last couple of years for a leak. Not sure if there were any other updates or not. Quote Link to comment Share on other sites More sharing options...
midlifeflyer Posted December 2, 2022 Report Share Posted December 2, 2022 (edited) On 11/29/2022 at 10:28 PM, PMcClure said: For Hot Start, I use the following: Throttle Full Mixture Off Prime 10 sec on Low or 5 seconds on High Mixture full Close throttle then open to 3-4 half turns Crank While cranking, turn throttle slowly in until engine catches Reduce throttle to idle Can you or someone talk a bit about this part? I originally learned the general method in a Bonanza - and the fuel circulation /line cooling reason - in a Bonanza. But with a difference. I don't have the IO-550 manual handy but the TCM operation manual for the IO-470, the IO-520, and the TIO550 are consistent in recommending that the initial cooling/prevention of vapor lock sequence be done with the throttle closed. This is the one from the TIO-550. Edit: found the IO-550 manual. Same as this Edited December 2, 2022 by midlifeflyer Quote Link to comment Share on other sites More sharing options...
PMcClure Posted December 3, 2022 Report Share Posted December 3, 2022 5 hours ago, midlifeflyer said: Can you or someone talk a bit about this part? I originally learned the general method in a Bonanza - and the fuel circulation /line cooling reason - in a Bonanza. But with a difference. I don't have the IO-550 manual handy but the TCM operation manual for the IO-470, the IO-520, and the TIO550 are consistent in recommending that the initial cooling/prevention of vapor lock sequence be done with the throttle closed. This is the one from the TIO-550. Edit: found the IO-550 manual. Same as this I don't have anything else to add, except that I did learn the procedure I report above in a Turbo TIO-520 Bonanza and carried it over to the Ovation and that it works for me every time. I do turn the throttle in while starting and it usually catches by the 1st or 2nd half turn. Quote Link to comment Share on other sites More sharing options...
carusoam Posted December 27, 2022 Report Share Posted December 27, 2022 For fuel circulation with the IO550…. mixture out, throttle in, pump on… The mixture out, keeps fuel from going to the engine… Throttle in, maximizes fuel going through the system… Pump, hi or Lo selects how much fuel you want to flow… in the end, the FF instrument will verify what you are doing. The FF instrument is mounted on the firewall, so it sees the fuel long before it gets to the mixture control… Best regards, -a- Quote Link to comment Share on other sites More sharing options...
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