Figuring out accelerate go

Discussion in 'Hangar Talk' started by Joffreyyy, Dec 6, 2017.

  1. Joffreyyy

    Joffreyyy Pre-Flight

    Joined:
    Mar 29, 2015
    Messages:
    64
    Display Name:

    Display name:
    Joffreyyy
    If I do ROC / TAS x .95 I get the gradient let’s say it’s 4.1 how do I figure out how many feet it would take to clear 50 foot obstacle

    I’m assuming it would be 50 / 4.1 x 100 to see how many feet it would take

    Or how would I figure out takeoff for single engine with no accelerate go distance for single engine
     
  2. Sac Arrow

    Sac Arrow Touchdown! Greaser!

    Joined:
    May 11, 2010
    Messages:
    15,171
    Location:
    Oakland, CA
    Display Name:

    Display name:
    Eight Balla
    Firewall it and hope for the best.
     
    Tyjay30, Cooter and 455 Bravo Uniform like this.
  3. MauleSkinner

    MauleSkinner En-Route

    Joined:
    Oct 25, 2005
    Messages:
    4,436
    Display Name:

    Display name:
    MauleSkinner
    Editing for revised knowlege... ;)

    50 = .041X
    Rearrange to find X

    X = 50/.041=1219 feet after liftoff.

    Somebody check my math. ;)
     
    Last edited: Dec 6, 2017
  4. dmspilot

    dmspilot En-Route

    Joined:
    Oct 20, 2006
    Messages:
    2,906
    Display Name:

    Display name:
    dmspilot
    4.1 what? Feet per mile?

    Where did you get that formula and what is the 0.95 for?
     
  5. Joffreyyy

    Joffreyyy Pre-Flight

    Joined:
    Mar 29, 2015
    Messages:
    64
    Display Name:

    Display name:
    Joffreyyy
    The poh has a formula that I listed above to figure out % gradient but does not give a accelerate go distance not sure why .95 that’s just what it says
     
  6. dmspilot

    dmspilot En-Route

    Joined:
    Oct 20, 2006
    Messages:
    2,906
    Display Name:

    Display name:
    dmspilot
    Oh, 4.1% makes more sense. So the gradient is actually 0.041.

    50'/0.041 = 1220'
     
  7. Joffreyyy

    Joffreyyy Pre-Flight

    Joined:
    Mar 29, 2015
    Messages:
    64
    Display Name:

    Display name:
    Joffreyyy
    Ok that makes sense to me thanks thats what I thought just wanted to confirm
     
  8. CC268

    CC268 En-Route

    Joined:
    Nov 4, 2015
    Messages:
    4,926
    Display Name:

    Display name:
    CC268
    Kick the tires light the fires
     
  9. Lachlan

    Lachlan Pattern Altitude

    Joined:
    Sep 23, 2015
    Messages:
    2,297
    Location:
    North Creek, NY
    Display Name:

    Display name:
    Lachlan
    That phrase is most appropriate for the full time rv thread.
     
    mscard88 likes this.
  10. CC268

    CC268 En-Route

    Joined:
    Nov 4, 2015
    Messages:
    4,926
    Display Name:

    Display name:
    CC268
    Lol :D
     
  11. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser!

    Joined:
    Jun 7, 2008
    Messages:
    10,579
    Location:
    DXO124009
    Display Name:

    Display name:
    Light and Sporty Guy
    edit: number is expressed as percent.
    Never mind.
     
    Last edited: Dec 6, 2017
  12. MauleSkinner

    MauleSkinner En-Route

    Joined:
    Oct 25, 2005
    Messages:
    4,436
    Display Name:

    Display name:
    MauleSkinner
    4.1 is percent...4.1 feet up per 100 feet forward.

    As far as the other math, 100 ft/minute is just about 1 knot (100 ft/1 minute)(60 minutes/1 hour) =6000 ft/minute...6076 ft/minute is one knot. The .95 may be factoring that plus the fact that the airplane doesn't instantaneously transition from on the runway to a stable climb gradient...there's a little curvature at the bottom. You'd have to ask the manufacturer exactly how they came up with it, however.

    @Joffreyyy ...what airplane are you working with?
     
  13. Clark1961

    Clark1961 Touchdown! Greaser!

    Joined:
    Jun 7, 2008
    Messages:
    17,746
    Display Name:

    Display name:
    Display name:
    If’n y’all be thinkin on clearing an obstacle perhaps y’all best be using ground speed.

    Jus sayin
     
    denverpilot likes this.
  14. Capt. Geoffrey Thorpe

    Capt. Geoffrey Thorpe Touchdown! Greaser!

    Joined:
    Jun 7, 2008
    Messages:
    10,579
    Location:
    DXO124009
    Display Name:

    Display name:
    Light and Sporty Guy
    Yea, I see that I misplaced the decimal point.
     
  15. MauleSkinner

    MauleSkinner En-Route

    Joined:
    Oct 25, 2005
    Messages:
    4,436
    Display Name:

    Display name:
    MauleSkinner
    True...hopefully the OP has figured that out across the board, because based on the way the manufacturer calculates this, I'd bet there's no wind compensation in any of the performance data.

    Or...just takeoff into the wind. ;)
     
  16. mscard88

    mscard88 Touchdown! Greaser!

    Joined:
    Oct 1, 2015
    Messages:
    22,892
    Location:
    Alabama
    Display Name:

    Display name:
    Mark
    I believe performance charts in the POH account for headwind or tailwind. It's not GS but I think close enough for that phase of flight.
     
  17. MauleSkinner

    MauleSkinner En-Route

    Joined:
    Oct 25, 2005
    Messages:
    4,436
    Display Name:

    Display name:
    MauleSkinner
    Depends on the POH and how old it is.
     
    denverpilot likes this.
  18. mscard88

    mscard88 Touchdown! Greaser!

    Joined:
    Oct 1, 2015
    Messages:
    22,892
    Location:
    Alabama
    Display Name:

    Display name:
    Mark
    True, plus the numbers are best case, test or factory pilot, new plane/engine, etc.
     
  19. Ted DuPuis

    Ted DuPuis Administrator Management Council Member

    Joined:
    Oct 9, 2007
    Messages:
    23,211
    Location:
    Paola, KS
    Display Name:

    Display name:
    iBanYou
    What aircraft is this for?
     
  20. mscard88

    mscard88 Touchdown! Greaser!

    Joined:
    Oct 1, 2015
    Messages:
    22,892
    Location:
    Alabama
    Display Name:

    Display name:
    Mark
    Cessna 150 :biggrin:
     
    Ted DuPuis likes this.
  21. luvflyin

    luvflyin Final Approach

    Joined:
    May 8, 2015
    Messages:
    5,343
    Location:
    Vancouver, WA
    Display Name:

    Display name:
    Luvflyin
    There was something around here awhile back. Not exactly what the question is here I think, but it was an abort or go decision. Something like reaching a % of Vx by a % of runway length. Like if Vx is 70 knots and the runway is 3000 feet, you better be be going 50 knots by the 2 board.
     
  22. MauleSkinner

    MauleSkinner En-Route

    Joined:
    Oct 25, 2005
    Messages:
    4,436
    Display Name:

    Display name:
    MauleSkinner
    The 50/70 rule is 70% of your liftoff speed by 50% of the runway...that only applies to ground roll for takeoff, and does nothing for you regarding either aborting safely or climbing.
     
    denverpilot likes this.
  23. luvflyin

    luvflyin Final Approach

    Joined:
    May 8, 2015
    Messages:
    5,343
    Location:
    Vancouver, WA
    Display Name:

    Display name:
    Luvflyin
    That was it
     
  24. denverpilot

    denverpilot Taxi to Parking

    Joined:
    Nov 8, 2009
    Messages:
    48,653
    Location:
    Denver, CO
    Display Name:

    Display name:
    DenverPilot
    If you get a bird strike from behind, the additional acceleration will help you just clear the trees at the end. LOL. :)
     
    mscard88 likes this.
  25. ARFlyer

    ARFlyer En-Route

    Joined:
    Dec 31, 2011
    Messages:
    2,733
    Location:
    Central AR
    Display Name:

    Display name:
    ARFlyer
    Personally, I don't screw with Accelerate Go. The distances most of the time are laughable at best. My school had a home brew formula that always gave you like 7000-11000' of runway required.

    If I lose an engine in a prop I'm chopping and stopping. I'd rather hit the fence at 30 knots vs Blue Line while skipping my ass across the ground.
     
    denverpilot likes this.
  26. MauleSkinner

    MauleSkinner En-Route

    Joined:
    Oct 25, 2005
    Messages:
    4,436
    Display Name:

    Display name:
    MauleSkinner
    I figure it's important to know how bad it really is, so you're not tempted to fly on one. ;)

    I think there are a lot of pilots, right up into turboprops and jets, who have an unrealistic image of what their single-engine performance actually looks like.
     
    denverpilot likes this.
  27. Kritchlow

    Kritchlow Final Approach

    Joined:
    Dec 2, 2014
    Messages:
    5,811
    Display Name:

    Display name:
    Kritchlow
    Sorry, didn’t read all responses carefully.
    That said, perhaps you know something I don’t..??
    Accelerate go is a term for twin engine airplanes, usually part 25. It’s the point where you can lose an engine at V1, accelerate to Vr, and clear the departure threshold by 35 feet.
    Accelerate stop is the point where you accelerate to V1, lose an engine and can stop on the runway. There is a point where these two values are equal, and thats called “balanced field length”.

    I’ve never heard of any of those terms while talking about a part 23 single engine airplane.

    ETA: I guess you are talking about a twin??
    If it’s a light twin good luck figuring the numbers. I know part 25 publishes but don’t think part 23 does.
     
  28. Kritchlow

    Kritchlow Final Approach

    Joined:
    Dec 2, 2014
    Messages:
    5,811
    Display Name:

    Display name:
    Kritchlow
    A 4.1 is rise over run. Figure the distance between lift off and the obstacle. Multiply that by 4.1%.... sort of. If whatever you’re outclimbing is high enough you’ll need to figure your climb gradient at the higher altitude, and with a lower temperature. Possible taking winds into account (thinking Aspen). A real headache and nearly impossible to calculate accurately.
    It’s easier to default to worst case (toc) but then you may not make it. It gets super messy.
     
  29. MauleSkinner

    MauleSkinner En-Route

    Joined:
    Oct 25, 2005
    Messages:
    4,436
    Display Name:

    Display name:
    MauleSkinner
    The data definitely exists in the CAR3/Part 23 world, although I don't believe it's always required by those regs.
     
  30. Kritchlow

    Kritchlow Final Approach

    Joined:
    Dec 2, 2014
    Messages:
    5,811
    Display Name:

    Display name:
    Kritchlow
    I know below 6,000 lbs it’s not required. Even above that I’m not sure if they have to publish it.
     
  31. MauleSkinner

    MauleSkinner En-Route

    Joined:
    Oct 25, 2005
    Messages:
    4,436
    Display Name:

    Display name:
    MauleSkinner
    Yeah, I'm not sure of the details of when it's required, but I know Barons (55 and 58 models, both under 6000 lbs) have always had the data in the POH.
     
  32. Kritchlow

    Kritchlow Final Approach

    Joined:
    Dec 2, 2014
    Messages:
    5,811
    Display Name:

    Display name:
    Kritchlow
    They publish accelerate go in a baron manual..??
    Never knew that, and I have significant time in a baron. Always thought the performance was just normal takeoff numbers.
     
  33. dmspilot

    dmspilot En-Route

    Joined:
    Oct 20, 2006
    Messages:
    2,906
    Display Name:

    Display name:
    dmspilot
    The Duchess (BE-76) has an Accelerate-Go chart as well.
     
  34. Kritchlow

    Kritchlow Final Approach

    Joined:
    Dec 2, 2014
    Messages:
    5,811
    Display Name:

    Display name:
    Kritchlow
    How heavy is that airplane?

    I’ve never seen ANY airplane with an accelerate go chart. Certainly not saying you are wrong as I’ve never flown a dutches.

    I’m typed in several Jets and all have charts... they are the longest of accelerate go, accelerate stop, or take off +15%.
    That covers all scenarios.

    If your airplane publishes accelerate go, than it must at least publish accelerate stop.
    Why publish two charts?? Publish the most restrictive makes sense imo.
     
  35. MauleSkinner

    MauleSkinner En-Route

    Joined:
    Oct 25, 2005
    Messages:
    4,436
    Display Name:

    Display name:
    MauleSkinner
    Accelerate-stop charts are also included, but you're not required to have accelerate-go and accelerate-stop distances available for takeoff in light twins--only two-engine takeoff. More than likely, accelerate-go would be limiting, and would be substantially longer than the runway unless you're approaching 10,000 feet of runway. That's one of the reasons Part 25 airplanes are demonstrably safer than light twins.

    At my last King Air job, the pilots agreed to require accelerate-stop distance for all takeoffs, but accelerate-go was still too long to be a reasonable requirement. In fact, the Beech chose V1 to bias accelerate-stop distances, and therefore accelerate-go is quite ugly. The King Air 250 finally provides the ability to adjust V1 like most Part 25 airplanes, but we still adjusted it for stopping distance (lower V1, obviously) and carried a light twin Plan B in our back pocket.
     
  36. JCranford

    JCranford Pattern Altitude

    Joined:
    Mar 8, 2015
    Messages:
    2,214
    Location:
    North TX
    Display Name:

    Display name:
    JCranford
    53, the answer is 53
     
  37. dmspilot

    dmspilot En-Route

    Joined:
    Oct 20, 2006
    Messages:
    2,906
    Display Name:

    Display name:
    dmspilot
    http://lmgtfy.com/?q=how+heavy+is+a+beechcraft+duchess

    Yes, it also has an accelerate-stop chart.

    During my ME training, my instructor wanted me to calculate accelerate-stop for each flight. We didn't bother with accelerate-go.