Speed Calculation

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EMB505
Posts: 4
Joined: Thu Nov 10, 2016 7:21 pm

Re: Speed Calculation

Post by EMB505 »

I have a 170B with O-300, the Horton STOL, and the seaplane prop. With 20* flaps at 5200' elevation it takes 900-1000' to get off the ground (3/4 fuel and two people). At 7500' I can barely get 90 mph indicated out of it. The only thing I can compare it to is a 67' 172 and it was 18 years ago so I don't know if that is reasonable performance or if the STOL kit and or the prop are hampering the cruise performance.
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ghostflyer
Posts: 1390
Joined: Mon Apr 21, 2008 3:06 am

Re: Speed Calculation

Post by ghostflyer »

EMB505 , I think something isn't right with your figures. Maybe the ASI is needing a technical wack or the pneumatic lines are leaking . I see totally different figures at that height .
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pdb
Posts: 466
Joined: Tue Apr 23, 2002 3:39 am

Re: Speed Calculation

Post by pdb »

EMB505 wrote: At 7500' I can barely get 90 mph indicated out of it. The only thing I can compare it to is a 67' 172 and it was 18 years ago so I don't know if that is reasonable performance or if the STOL kit and or the prop are hampering the cruise performance.
I am not sure you have a problem. I have an 80/42 prop and usually fly close to sea level at low density altitudes where I barely get 95 mph IAS. Its like I am driving around in 1st gear everywhere but my take offs are short.

Although I generally never fly high, I would have to imagine that even if I leaned it out correctly at 7,500', my IAS would be somewhere in your range. Of course, TAS will increase over IAS about 2% for every 1,000 foot increase in altitude so your TAS will be more respectable.
Pete Brown
Anchorage, Alaska
N4563C 1953 170B
http://farm3.staticflickr.com/2366/2527 ... 4e43_b.jpg
EMB505
Posts: 4
Joined: Thu Nov 10, 2016 7:21 pm

Re: Speed Calculation

Post by EMB505 »

I have given the ASI the mechanic tap and the needle would jump a couple of MPH. My TAS is only about 95 MPH and that's about what the GPS is showing also so I think the ASI is accurate.

I was thinking I should be doing about 105 TAS.

It definitely feels like 1st gear
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Joe Moilanen
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Joined: Sun Dec 28, 2003 5:45 am

Re: Speed Calculation

Post by Joe Moilanen »

I get 105-108 mph with my 8043

Joe
EMB505
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Joined: Thu Nov 10, 2016 7:21 pm

Re: Speed Calculation

Post by EMB505 »

Joe Moilanen wrote:I get 105-108 mph with my 8043

Joe
At what altitude? Do you have aSTOL kit?
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pdb
Posts: 466
Joined: Tue Apr 23, 2002 3:39 am

Re: Speed Calculation

Post by pdb »

pdb wrote:
EMB505 wrote:
I am not sure you have a problem. I have an 80/42 prop and usually fly close to sea level at low density altitudes where I barely get 95 mph IAS. Its like I am driving around in 1st gear everywhere but my take offs are short.
I should have noted that I have a stock wing with VGs, bubble side windows, and 8:50s.
Pete Brown
Anchorage, Alaska
N4563C 1953 170B
http://farm3.staticflickr.com/2366/2527 ... 4e43_b.jpg
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Joe Moilanen
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Joined: Sun Dec 28, 2003 5:45 am

Re: Speed Calculation

Post by Joe Moilanen »

EMB505 wrote:
Joe Moilanen wrote:I get 105-108 mph with my 8043

Joe
At what altitude? Do you have aSTOL kit?
I have a Sportsmans STOL kit. Those #'s were without it, I think I picked up a couple mph since I installed it.
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