Stuck at work--need takeoff/landing distances for a 172 please

[Yossarian]

Excuse my laziness but if anyone feels like checking some distances for
me I would be greatly appreciative ;)

172SP, fully loaded, 73' field elevation (Bermuda Dunes, CA), 120
degrees F, paved runway, assume no wind.

I have a feeling the density altitude isn't going to make this feasible.

[Peter R.]

Yossarian > wrote:

> Excuse my laziness but if anyone feels like checking some distances for
> me I would be greatly appreciative ;)
>
> 172SP, fully loaded, 73' field elevation (Bermuda Dunes, CA), 120
> degrees F, paved runway, assume no wind.
>
> I have a feeling the density altitude isn't going to make this feasible.

Assuming a relatively low dew point (a safe assumption for the desert
southwest) and using Palm Springs altimeter setting, I am only arriving at
a density altitude of around 4,200 ft MSL.

Also being "stuck at work," I do not have access to my 172SP PIM with the
take off distances. However, I recall that 4,200 feet DA is definitely
do-able for a fully loaded 172SP on a 5,000 ft runway, which is the runway
length at Bermuda Dunes.

Of course, I would not expect you to operate your aircraft based on this
information alone. :)

What DA do you come up with?



--
Peter
























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[Peter Clark]

On 13 Jul 2005 12:19:23 -0700, "Yossarian" >
wrote:

>Excuse my laziness but if anyone feels like checking some distances for
>me I would be greatly appreciative ;)
>
>172SP, fully loaded, 73' field elevation (Bermuda Dunes, CA), 120
>degrees F, paved runway, assume no wind.
>
>I have a feeling the density altitude isn't going to make this feasible.

Partial listing, Short-field performance (from 172SP IM), 2550lb:

ground roll/clear 50' obstacle. Pressure altitudes.

temp 0deg 10deg 20deg 30deg 40deg C

SL 860/1465 925/1575 995/1690 1070/1810 1150/1945
1K 940/1600 1010/1720 1090/1850 1170/1990 1260/2135
2K 1025/1755 1110/1890 1195/2035 1285/2190 1380/2355
3K 1125/1925 1215/2080 1310/2240 1410/2420 1515/2605

decrease distance 10% for each 9 knot headwind. Increase distance 10%
for each 2knots of tailwind up to 10 knots.

Luck.

[Peter Clark]

On Wed, 13 Jul 2005 15:39:35 -0400, "Peter R."
> wrote:

>Yossarian > wrote:
>
>> Excuse my laziness but if anyone feels like checking some distances for
>> me I would be greatly appreciative ;)
>>
>> 172SP, fully loaded, 73' field elevation (Bermuda Dunes, CA), 120
>> degrees F, paved runway, assume no wind.
>>
>> I have a feeling the density altitude isn't going to make this feasible.
>
>Assuming a relatively low dew point (a safe assumption for the desert
>southwest) and using Palm Springs altimeter setting, I am only arriving at
>a density altitude of around 4,200 ft MSL.
>
>Also being "stuck at work," I do not have access to my 172SP PIM with the
>take off distances. However, I recall that 4,200 feet DA is definitely
>do-able for a fully loaded 172SP on a 5,000 ft runway, which is the runway
>length at Bermuda Dunes.
>
>Of course, I would not expect you to operate your aircraft based on this
>information alone. :)
>
>What DA do you come up with?

Assuming we're talking about KUDD, 73' elevation, 40 deg C temp,
altimeter 29.79, I come up with pressure altitude of 190' and density
alt of 3050.

[Peter R.]

Peter Clark > wrote:

> Assuming we're talking about KUDD, 73' elevation, 40 deg C temp,
> altimeter 29.79, I come up with pressure altitude of 190' and density
> alt of 3050.

Hmmm, I keep arriving at a DA about 1200 feet higher. Cross checking this
with several DA calculator websites confirms about 4,200 ft or so.

--
Peter
























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[Peter R.]

"Peter R." > wrote:

>> Assuming we're talking about KUDD, 73' elevation, 40 deg C temp,
>> altimeter 29.79, I come up with pressure altitude of 190' and density
>> alt of 3050.
>
> Hmmm, I keep arriving at a DA about 1200 feet higher. Cross checking this
> with several DA calculator websites confirms about 4,200 ft or so.

Nevermind, I see the discrepancy. The OP was asking about 120 degrees F,
which is about 49 degrees C. That was the temp I was using.

--
Peter
























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[Peter Clark]

On Wed, 13 Jul 2005 15:58:46 -0400, "Peter R."
> wrote:

>Peter Clark > wrote:
>
>> Assuming we're talking about KUDD, 73' elevation, 40 deg C temp,
>> altimeter 29.79, I come up with pressure altitude of 190' and density
>> alt of 3050.
>
>Hmmm, I keep arriving at a DA about 1200 feet higher. Cross checking this
>with several DA calculator websites confirms about 4,200 ft or so.

Hm. I'm using
http://www.asa2fly.com/category1.asp?SID=1&Category_ID=179

Perhaps there's a code error in their online CX-2 program? Or maybe
I'm doing something wrong. Flight/Alt/Press alt, give it field
elevation and altimeter. Flight/alt/Density alt, it auto-feeds the
press alt over, give it temp, comes with 3049. So does my real E6-B
that I just dug out? Looks like you need a pressure alt of 1500' or
so to get a density alt of 4200' or so.

[Peter Clark]

On Wed, 13 Jul 2005 16:02:20 -0400, "Peter R."
> wrote:

>"Peter R." > wrote:
>
>>> Assuming we're talking about KUDD, 73' elevation, 40 deg C temp,
>>> altimeter 29.79, I come up with pressure altitude of 190' and density
>>> alt of 3050.
>>
>> Hmmm, I keep arriving at a DA about 1200 feet higher. Cross checking this
>> with several DA calculator websites confirms about 4,200 ft or so.
>
>Nevermind, I see the discrepancy. The OP was asking about 120 degrees F,
>which is about 49 degrees C. That was the temp I was using.

Yea, my bad. They only print the chart to 40 so that number got stuck
in my head. 49C comes out with 4k density alt. So extrapolating from
the 40C column at 4K comes out with 1770/3085 for roll/50' obst.

[Ray]

> Yea, my bad. They only print the chart to 40 so that number got stuck
> in my head. 49C comes out with 4k density alt. So extrapolating from
> the 40C column at 4K comes out with 1770/3085 for roll/50' obst.

You don't need to account for density altitude in this case since the POH is
already giving the performance numbers at the non-standard temperature. By
using the numbers for 40C and 4000ft you're essentially double counting the
effect of higher temperature and far underestimating the performance. Since
the chart only goes to 40C you still have to extrapolate to the higher
temperature and you have to make a guess about the pressure altitude but in
the end the distance to clear a 50' obstacle should still be under 2000 ft.

- Ray

[Peter Clark]

On Wed, 13 Jul 2005 14:48:27 -0700, "Ray" > wrote:

>> Yea, my bad. They only print the chart to 40 so that number got stuck
>> in my head. 49C comes out with 4k density alt. So extrapolating from
>> the 40C column at 4K comes out with 1770/3085 for roll/50' obst.
>
>You don't need to account for density altitude in this case since the POH is
>already giving the performance numbers at the non-standard temperature. By
>using the numbers for 40C and 4000ft you're essentially double counting the
>effect of higher temperature and far underestimating the performance. Since
>the chart only goes to 40C you still have to extrapolate to the higher
>temperature and you have to make a guess about the pressure altitude but in
>the end the distance to clear a 50' obstacle should still be under 2000 ft.

Yea, I was thinking that since the chart lists pressure altitude on
the left column, but figured I'd throw out the number for the 4K
pressure 50C extrapolation and let the original poster do decide what
to do with the data.

[Peter Duniho]

"Ray" > wrote in message
...
> [...]
> Since
> the chart only goes to 40C you still have to extrapolate to the higher
> temperature

Or, they can use the density altitude, but pick performance figures for
standard temp from the POH. No extrapolation necessary in that case.

Pete

[Yossarian]

wow! thanks Peter (and others who contributed). now the hard part will
be getting 4 adults, a small dog, and assorted stuff below the useful
load limit.

Peter Clark > wrote in
:

> On 13 Jul 2005 12:19:23 -0700, "Yossarian" >
> wrote:
>
>>Excuse my laziness but if anyone feels like checking some distances for
>>me I would be greatly appreciative ;)
>>
>>172SP, fully loaded, 73' field elevation (Bermuda Dunes, CA), 120
>>degrees F, paved runway, assume no wind.
>>
>>I have a feeling the density altitude isn't going to make this
feasible.
>
> Partial listing, Short-field performance (from 172SP IM), 2550lb:
>
> ground roll/clear 50' obstacle. Pressure altitudes.
>
> temp 0deg 10deg 20deg 30deg 40deg C
>
> SL 860/1465 925/1575 995/1690 1070/1810 1150/1945
> 1K 940/1600 1010/1720 1090/1850 1170/1990 1260/2135
> 2K 1025/1755 1110/1890 1195/2035 1285/2190 1380/2355
> 3K 1125/1925 1215/2080 1310/2240 1410/2420 1515/2605
>
> decrease distance 10% for each 9 knot headwind. Increase distance 10%
> for each 2knots of tailwind up to 10 knots.
>
> Luck.
>
>

[Corky Scott]

On Wed, 13 Jul 2005 20:34:18 -0500, Yossarian >
wrote:

>wow! thanks Peter (and others who contributed). now the hard part will
>be getting 4 adults, a small dog, and assorted stuff below the useful
>load limit.

Half full fuel tanks?

Corky Scott