Cirrus Fuel Boost Pump and NTSB

Discussion in 'Hangar Talk' started by Tantalum, Apr 22, 2022.

  1. Tantalum

    Tantalum Final Approach

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    From Flying https://www.flyingmag.com/ntsb-to-cirrus-address-fuel-boost-pump-issues-with-sr22t/

    Emphasis mine
    "
    After investigating six takeoff accidents involving uncommanded loss of engine power in Cirrus SR22T, the National Transportation Safety Board is recommending the aircraft manufacturer conduct a Functional Hazard Assessment (FHA) to address the issue and mitigate the risk.

    According to a report issued on April 12 by the NTSB, the six accidents were the result of excessive fuel flow in the SR22T, which caused engine failure during climb out. The accidents, which happened between 2017 and 2019, resulted in three deaths and nine persons injured.

    During the accident investigations, the NTSB removed the recoverable data monitors from the accident aircraft and determined that in each case the aircraft indicated an excessively high fuel flow rate, ranging from 42.2 to 50.1 gallons per hour, just before the engine lost power.
    ...
    The excessive fuel overloads the engine, similarly to the way chugging a beverage makes a person choke.
    ...
    "


    My issues
    (1) for a publication by pilots, for pilots, saying that an over-rich situations is "overloading" the engine and comparing it to chugging a drink is absurd. Sad. This is CNN level aviation reporting.

    (2) in my (not so) humble opinion this is really on the pilots.. during your takeoff run you should be watching the engine page and looking for abnormalities, aborting if they arise. If you get a fuel flow surge already in the air, there's a red knob, lean the engine appropriately. This comes back to training, I worry a lot of people go through things rote "takeoff = red knob all the way forward" without really thinking about or understanding what's happening

    Turbo Cirri are known to be finnicky with fuel flow, and during initial climb, and climb to cruise, you have to monitor it closely

    /end mini rant
     
  2. RudyP

    RudyP Cleared for Takeoff

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    No major disagreement on my end - especially on your first point - but the fuel pumps in SR22s are notoriously finicky/failure prone. I lost track of how many replacements/rebuilds I went through on my SR22TN but it was something like 3 main engine driven pumps and 2 electric boost pumps and at best it was never rock solid on maintaining consistent fuel flow. That’s why people set them up to run richer than they are supposed to so you have some margin that you can adjust with the mixture knob back but then you have to pay attention…
     
    Last edited: Apr 22, 2022
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  3. Tantalum

    Tantalum Final Approach

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    and that's just it!
     
  4. PaulS

    PaulS Touchdown! Greaser!

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    So two out of three problems were operator error. It seems to me with the Garmin automation, a red warning of too much fuel flow would help with this, plus training. I also suspect the pilots who had the operator error issues were not POH readers and probably not well trained.

    It seems that Garmin/Cirrus has addressed this, but the fix has issues, which were found out by pilots operating the system improperly.... can't make this stuff up
     
  5. MonkeyClaw

    MonkeyClaw Pre-takeoff checklist

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    The issue is that often a hiccup in the fuel flow (for whatever reason) can cause the auxiliary pump to kick on (it is initially set to 'armed' and not actually running). If the primary pump didn't fail, but only had a pause for some reason, you now have both fuel pumps running at the same time and it floods the engine. Columbias can have the same thing happen. The common suggestion in Columbias is now to NOT arm the backup fuel pump, but be 'at the ready' in case there is an issue. The flooding happens very quickly. Luckily the Columbia fleet hasn't lost many (any?) due to this issue.
     
  6. MountainDude

    MountainDude Pre-takeoff checklist PoA Supporter

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    You pay $1M for a plane, then have to be familiar with a problem that is not described in the POH, happens rarely and randomly, and during a busy climb-out phase.
    Hmm.
     
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  7. dmspilot

    dmspilot Final Approach

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    Does this only affect the turbo model?
     
  8. weilke

    weilke Touchdown! Greaser! PoA Supporter

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    1M plane and your fuel flow is governend by an interplay of mechanical pumps, electrical pumps and manual levers. Bizarre.

    This is not a Cirrus specific issue, this is a turbo Continental specific issue. We had the same struggle in our turbo Bo with the 520-UB. If you kicked in the aux pump to suppress bubbles you had to pull back the mixture to keep it from flooding. If you didn't get that right quick enough, you would lose engine power.
     
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  9. Tantalum

    Tantalum Final Approach

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    I mean, regardless what you pay for an airplane you should understand proper fuel flow and engine management technique
     
  10. TrueCourse

    TrueCourse Line Up and Wait

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    I thought it IS described in the POH. Did the Service Advisory not end up as a revision to the POH? Then again, not everyone updates their POH to the latest edition.
     
  11. bbarrett

    bbarrett Filing Flight Plan

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    Sure, but in 2022, the fact that we're using fuel metering systems that can't automatically adjust to differing input pressures is kind of absurd. The Continental fuel injection system may be simple, but it's also not very accommodating to pressure changes (like those from an electric pump kicking on / off).
     
  12. Kenny Phillips

    Kenny Phillips En-Route

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    Yes. Fuel pressure regulators aren't unheard of in aviation.
     
  13. RudyP

    RudyP Cleared for Takeoff

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    Exactly. I understand the economics of GA piston being a tiny market with too little $$$ for anyone to have a major incentive to actually embrace semi-modern technology but this 1930s tractor technology that you have to put up with is a big reason I went to the turbine world where the economics support FADEC, reliable fuel systems, accurate gauges and myriad other things that have been standard on cheap cars since the 90s but are still MIA from $1M brand new planes in 2022.
     
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  14. hindsight2020

    hindsight2020 Final Approach

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    .... welcome to "certified" aviation for the last 30 years?

    Seriously, it's not like this is automotive consumer protection economies of scale, if that's what $1M airplane buyers feel entitled to. At this juncture I thought it was rather stipulated one's a glutton for punishment ("captive audience" if you prefer) by choosing to sponsor the entire pricing model of this sector of aviation in the first place. It's not like the internet hasn't existed and provided forewarning for half the time this has been going on.

    ETA: just to be clear, I'm not defending it. I think it's a bum deal and I have purposely underpurchased in this hobby in order to minimize my value-loss in mx, parts and regulatory choke, while still gaining access to a second row. My next phase doesn't require one and thus EAB liberates me from much of this nonsense.
     
    Last edited: Apr 23, 2022
  15. Tantalum

    Tantalum Final Approach

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    Totally agree. Don't even get me started on the dinky state of piston aviation GA tech
     
  16. NoHeat

    NoHeat En-Route

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    Yes.