# Figuring out accelerate go

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

1. ### JoffreyyyPre-Flight

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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 ArrowTouchdown! Greaser!

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Firewall it and hope for the best.

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3. ### MauleSkinnerEn-Route

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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. ### dmspilotPattern Altitude

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4.1 what? Feet per mile?

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

5. ### JoffreyyyPre-Flight

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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. ### dmspilotPattern Altitude

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Oh, 4.1% makes more sense. So the gradient is actually 0.041.

50'/0.041 = 1220'

7. ### JoffreyyyPre-Flight

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Ok that makes sense to me thanks thats what I thought just wanted to confirm

8. ### CC268En-Route

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Kick the tires light the fires

9. ### LachlanCleared for Takeoff

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That phrase is most appropriate for the full time rv thread.

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10. ### CC268En-Route

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Lol

11. ### Capt. Geoffrey ThorpeFinal ApproachPoA Supporter

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edit: number is expressed as percent.
Never mind.

Last edited: Dec 6, 2017
12. ### MauleSkinnerEn-Route

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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. ### Clark1961Touchdown! Greaser!

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

Jus sayin

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14. ### Capt. Geoffrey ThorpeFinal ApproachPoA Supporter

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Yea, I see that I misplaced the decimal point.

15. ### MauleSkinnerEn-Route

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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. ### mscard88Touchdown! Greaser!

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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. ### MauleSkinnerEn-Route

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Depends on the POH and how old it is.

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18. ### mscard88Touchdown! Greaser!

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True, plus the numbers are best case, test or factory pilot, new plane/engine, etc.

19. ### Ted DuPuisAdministratorManagement Council Member

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What aircraft is this for?

20. ### mscard88Touchdown! Greaser!

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Cessna 150

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21. ### luvflyinEn-RoutePoA Supporter

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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. ### MauleSkinnerEn-Route

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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.

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23. ### luvflyinEn-RoutePoA Supporter

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That was it

24. ### denverpilotTaxi to Parking

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If you get a bird strike from behind, the additional acceleration will help you just clear the trees at the end. LOL.

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25. ### ARFlyerEn-Route

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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.

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26. ### MauleSkinnerEn-Route

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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.

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27. ### KritchlowFinal Approach

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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. ### KritchlowFinal Approach

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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. ### MauleSkinnerEn-Route

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

30. ### KritchlowFinal Approach

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I know below 6,000 lbs it’s not required. Even above that I’m not sure if they have to publish it.

31. ### MauleSkinnerEn-Route

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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. ### KritchlowFinal Approach

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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. ### dmspilotPattern Altitude

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The Duchess (BE-76) has an Accelerate-Go chart as well.

34. ### KritchlowFinal Approach

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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. ### MauleSkinnerEn-Route

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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. ### JCranfordPattern Altitude

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37. ### dmspilotPattern Altitude

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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.