Keeping Oil Off the Windshield after Engine Failure

Discussion in 'Firewall Forward / Props / Fuel system' started by SVSUSteve, Sep 6, 2019.

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  1. Sep 6, 2019 #1

    SVSUSteve

    SVSUSteve

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    My wife is one of my volunteers in aviation safety research. She's entering data for me this morning between appointments with the clients at her law firm. She came across one of the cases where the crash was precipitated by an engine failure. The pilot reported to ATC that he had oil all over his windshield. They dropped into trees short of a field where an emergency landing could have been carried out. There was no evidence of the cowling being damaged before they hit the trees. She has the file so I don't remember the exact initial cause of the failure but I remember it involved the structure of the engine fracturing at some point.

    Her question to me was "Isn't there some way to design the hood of the plane (she didn't know the word "cowling") to keep that from happening?". Aside from making the cowling able to stay on and with a tight seal, I don't have a clue. She goes "Maybe those guys on the airplane forum with have some ideas?"

    Any ideas fellas?
     
  2. Sep 6, 2019 #2

    gtae07

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    Yeah, that's gonna be a tough one. Good sealing would probably help some and is a good idea for cooling and efficiency reasons, but seeping oil in a turbulent area of high airflow likes to get everywhere and I don't know if it would really be possible to fully seal something against seeping oil. A leak forward of the engine itself--think around the prop or forward seal on a Lycoming--might get past all the cowl sealing anyway.

    My take would be, seal your cowl/plenum well for cooling purposes, maintain your engine well, and focus on reducing the likelihood and consequences of other failures.



    I do remember an account from a guy on VAF who had such a failure and made good use of his EFIS and synthetic vision (he made a point to mention that) to get back on the ground.
     
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  3. Sep 6, 2019 #3

    SVSUSteve

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    Yeah. I am planning on being borderline obsessive about engine maintenance.

    I think I read that as well. I am already planning on having a MAX-VIZ infrared enhanced vision system on the plane so that might be a fallback option as well. It should be well clear of anywhere oil could wind up.
     
  4. Sep 6, 2019 #4

    wsimpso1

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    To fully solve this, we would need a better idea of how the oil gets from engine to windshield.

    My suspicion is that the oil sprays onto both the underside of the cowling and onto the front side of the firewall, then travels through the gap between cowl and fuselage and onto the windshield.

    Four paths make sense to me for this. And none of these can be new:
    • First two are to put a coaming onthe underside of the cowling and to put another coaming at the very top of the firewall. I imagine a little channel maybe 3/8 x 3/8 with the open side facing forward (underside of cowling) and facing down (on firewall). This will catch oil flowing toward the join, driven by under cowl air flows. They will only capture a small amount of oil unless you give them an outlet, say at the sides of the ship - then the majority of the oil will be diverted to stream down the sides of the ship.
    • Next is sealing the cowling-fusealge join. Oil mist and flame products will escape through whatever channels exist, so a continuous seal along the cowling-fuselage join area will have considerable value in keeping the windshield clear.
    • I do like using an EFIS with synthetic vision as a last resort. Allowing you to stay visual through such an emergency would probably work better in this sort of high workload high stress situation.
    I am waiting for folks to tell us if these have been executed in other aircraft and how well they have worked.

    Billski
     
  5. Sep 6, 2019 #5

    Pops

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    Make the cowling airtight. :)
     
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  6. Sep 6, 2019 #6

    Dana

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    Does it happen often enough that it's worth addressing?

    In a FMEA (Failure Modes and Effects Analysis), that'd be an numeric entry in the "occurence" column, from one for very unlikely to a ten for almost certain. That's multiplied by the "severity" number (ranging from no effect to certain death) and the "detection" number to get a RPN (Risk Priority Number)... you address the higher numbers first.

    When the oil hose let go on my Starduster, all the oil ended up on the bottom of the fuselage and lower wings (a huge mess), nothing at all on the windscreen. And a lot hit the exhaust making so much smoke that people were calling 911 before I even touched down.
     
  7. Sep 6, 2019 #7

    TFF

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    If a crank cracks or oil seal goes, The oil usually travels forward and gets slung by the prop blades. Low pressure behind the prop spinner makes it a no mans land usually. I have been involved with two cracked cranks and that is what happened with both.
     
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  8. Sep 6, 2019 #8

    Pops

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    One time I had a oil pressure sending unit break, I smelled hot oil as I seen the oil pressure gauge hit zero. About 5K above an airport over the nose. Lost 4 qts of oil at idle rpm to airport. All the oil was on firewall and the bottom of the fuselage, As Dana said, huge mess. Windshield clean. I shut down the engine on the runway as I flared to land. Got it towed to the ramp. NOT tarmac.
     
    Last edited: Sep 6, 2019
  9. Sep 6, 2019 #9

    Charles_says

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    Hey! Don't forget Charles Lindberg flew across the Atlantic without a windshield,at all! took off and landed without a forward view...
    So, they're just a convenience...?
     
  10. Sep 6, 2019 #10

    Charles_says

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    Of course....... He didn't have much air traffic at the time.....:rolleyes:
     
  11. Sep 6, 2019 #11

    Hot Wings

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    Another potential advantage of water cooling? Put the radiator aft and seal the engine compartment - leaving just enough circulation to keep the under cowl temperatures reasonable. Less air flow = less chance of oil migration.
     
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  12. Sep 6, 2019 #12

    Aerowerx

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    Fly in a constant crab?

    That is, cross-control so you are able to look out the side of the cockpit. Most of the oil would then be blown to the other side, I think.
     
  13. Sep 6, 2019 #13

    Dan Thomas

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    Cessna puts a baffle seal along the top and side of the firewall that contacts the cowling to help prevent this sort of thing. In most of the older airplanes that seal is shrunken and hard and not doing anything. It's a real pain to replace.

    And it wouldn't stop oil being flung off the prop hub. A bad crankshaft seal is the usual culprit, and the problem is often traced to a crankcase breather tube that's blocked for some reason, pressurizing the case and blowing that seal out. The tube might be coked up with carbon (which is why a check of it for airflow is on Cessna's inspection checklists) or it doesn't have a "whistle slot," a quarter-inch hole in the tube up some distance from the bottom of the firewall. It's there to prevent pressure buildup if the escaping moisture (from combustion blowby) freezes the end of the tube shut in cold weather. The tube's end hanging out in the breeze will do that. In Canada we often insulate that tube to keep the gases warm as they leave to help prevent freezup. Many airplanes came with the insulation, but it ages and cracks and starts falling off, so people rip it off, not knowing why it was there.

    Sometimes a constant-speed propeller blade seal will go, but if the prop is overhauled in accordance with manufacturer's recommendations, that's unlikely. McCauley usually wants that prop done every six years or at engine TBO, whichever comes first; in Canada, Transport allows a 10-year interval.

    Oil on the windshield is rare. There are other things that are more likely to kill you. Something like 90% of accidents are due to pilot error; get the right training and maintain a good attitude toward flying and you mitigate most of that risk. Money spent on training is more effective than money spent on extra precautions against airframe or engine failures, and the training sure weighs a lot less than all the extra doodads.
     
  14. Sep 6, 2019 #14

    Deuelly

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    Neither would you though once you declared an emergency. :eek:
     
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  15. Sep 7, 2019 #15

    Daleandee

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    Hope this isn't too over the top but they make Rain-X so ... how about someone invent a product and call it Oil-X ... o_O

    Dale
    N319WF
     
  16. Sep 7, 2019 #16

    Dan Thomas

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    Or wipers and windshield washer fluid made of solvent...
     
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  17. Sep 7, 2019 #17

    Mad MAC

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    Given the interesting range of possible sources of oil including a number that are really hard to prevent (crank seal failure followed by prop flinging of the oil or engine component through cowl being lead examples). Perhaps the best response is that it mostly likely still fly, so fly to a pre-selected area and pull the BRS (particularly if you are going to fit fire suppression). Noting that a leading killer of glider pilots is delaying the decision to land out until they run out of height to find somewhere good and that the SR22 flight manual response to just about all inflight emergencys is to pull the chute, possibly best to approach this one is the KISS principle.
     
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  18. Sep 7, 2019 #18

    TFF

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    The insurance logic for Cirrus pulling the BRS is simply math. Cost of one airplane and damage to what it lands on is way less than one death, when it comes to payout. Say $400,000 total vs about $2M a person. Now the crank I am familiar with cracking was on a Cirrus and they landed at closest airport. If he had gone another hour he would have surly used the chute.
     
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  19. Sep 7, 2019 #19

    Tiger Tim

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    It’s too late to make it a pusher, right?
     
  20. Sep 7, 2019 #20

    Himat

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    Pusher engine? Oil on the windscreen then spell serious trouble.;)

    With engine and prop up front the solution have already been forwarded. Seal the cowling and manage the airflow. Ideally, the air from the engine compartment should went to an area with a lower air pressure than all areas in front of the windscreen. I guess some car manufacturers spend a loot of wind tunnel hours to make sure rain and dust do follow the “right” path on the vehicle.
     

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