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Takeoff Performance Calcs w/ 2-Degree Upslope (AVX)


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I'm planning a fight to AVX (Catalina Island) this weekend.  I've been there before in other aircraft, but this is the first time in my Mooney (M20G).

Runway 22 has a 2-degree upslope.  I'm worried this may significantly affect my takeoff roll compared to book values (I'll be close to gross wt).  Any insight as to how much extra runway I can expect to use over book value?

Also, would appreciate any Mooney-specific tips for getting in/out of AVX.  I'm familiar with the downdrafts and runway condition.

Ryan

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14 minutes ago, dlmorris said:

Get yourself a Take-Off Computer and never guess again... I've had one in my flight bag for 20 years.

https://sportys.com/pilotshop/takeoff-performance-computer.html

  

That is handy.  Why isn't this built into Garmin Pilot and/or ForeFlight?  Or any app for that matter?

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29 minutes ago, aggiepilot04 said:

That is handy.  Why isn't this built into Garmin Pilot and/or ForeFlight?  Or any app for that matter?

I'll guess three reasons:

  • For the same reason you don't have this one. No significant demand. I think I had one years ago and never used it. And that was flying into mountain airports in Colorado. Heck, if this was a popular item, I'd expect to see the place littered with apps, spreadsheets, etc.
  • It's only a ballpark with no real consensus on the factor to use. If you do a search you will find references to  different numbers. Just as reasonable, and easier, to use a rule of thumb.
  • If it's in an app it's treated as gospel. 

 

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I have a Koch chart in my flight bag. Useful for calculating take off distance and rate of climb (esp. high-altitude airports at non-standard temps). I haven't had to deal with significant runway slope issues, but one can be a little conservative and add some margin, look at the airport environs and make sure you know where you are going and what the outs are.

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2 hours ago, kmyfm20s said:

The first half of the runway is uphill the second half is downhill. You will be off the ground before you hit the downhill. If you keep going past the end of the runway it will be like launching off an aircraft carrier. 

+1

i usually speed up in ground effect and avoid steep climbs.

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Keep in mind...

The OP is also flying the heaviest Power to weight ratio plane in the Mooney fleet.  Low on power, high on weight, and slow on acceleration.  Once off the ground, high on AOA until enough speed is gained...

departing at full gross, is going to use a long piece of runway.

Adding the effects of the uphill runway...

Also, Add in the effects of temperature/Density altitude at the time of departure... don't skip this step...

Make sure to take in account all that can be taken into account.

PP thoughts only, not a CFI...

Best regards,

-a-

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54 minutes ago, carusoam said:

Keep in mind...

The OP is also flying the heaviest Power to weight ratio plane in the Mooney fleet.  Low on power, high on weight, and slow on acceleration.  Once off the ground, high on AOA until enough speed is gained...

departing at full gross, is going to use a long piece of runway.

Adding the effects of the uphill runway...

Also, Add in the effects of temperature/Density altitude at the time of departure... don't skip this step...

Make sure to take in account all that can be taken into account.

PP thoughts only, not a CFI...

Best regards,

-a-

This is what I'm worried about. I don't want to be the pilot who added 20% to the book value and assumed it was enough.  Maybe I shouldn't be worried about this at all, but I have to prove it to myself first. 

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It should be nice and cool if you're going this weekend (between 58-64 deg). Just getting there should put you somewhat under gross, unless you took off over gross, as there is no gas at AVX (or you're bringing home a bunch of fish or lobster or something). There is almost always some wind to decrease the takeoff roll.  I took off there often close to gross in my C, plenty of runway. 

I might see you there; either going there or Friday harbor this weekend (one island or another).

Edited by jrwilson
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One of the things you can do is measure and compare your plane's performance to the book values.  You will need a POH for your plane for that.

there is an app for that...

Also know where the book values start to tail off from useability...

Measuring T/O distance can be done using CloudAhoy with a WAAS source like SkyRadar.  Collect data and compare to known values.

Other people do this the old fashioned way knowing distance markers along a familiar runway.

The last thing you want to do is guess that it will be OK.  This has a tendency to not work very well... the cost can be large.

Plan B:  you're on the roll. Things aren't working out. Know what your stopping distance is and the procedure to execute it....

A safety factor of 2X starts to make sense.  Know that IF it is a challenge to climb out of ground effect anything in the way like trees becomes a real problem...

what is the difference between your plane's Best T/O roll and it's worst, according to the POH?

PP ideas only, not a CFI...

Best regards,

-a-

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10 minutes ago, jrwilson said:

It should be nice and cool if you're going this weekend (between 58-64 deg). Just getting there should put you somewhat under gross, unless you took off over gross, as there is no gas at AVX (or you're bringing home a bunch of fish or lobster or something). There is almost always some wind to decrease the takeoff roll.  I took off there often close to gross in my C, plenty of runway. 

I might see you there; either going there or Friday harbor this weekend (one island or another).

Thanks. I'll shoot you a message once I know if/when I'm going. Would be nice to meet another MS pilot. 

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I'm not sure what airport your based out of but Lancaster is 2300' msl and KAVX is 1600'. Measure the distance it take you to get off the ground at your home airport. KAVX is 3000' long and sure to have comparable DA. If you don't pick up any weight in Catalina you will have a very good idea of what to expect.

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