Van's Air Force
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Speeds
- Thread starter Leargo
- Start date
Knots vs. mph
Ahhh...the eternal question!
As a trained Aeronautical Engineer, it was beaten in to me that the REAL aviation world always does things in knots, and my papers would be failed if i used any other units...
As a Commercial and Instrument Pilot, I have been trained to do everything in knots, because that is what the ATC world uses.
In the Flight operations world in which I live, we do everything in knots because that is the engineering standard (see first bullet above...)
Many people like to use mph because the numbers are bigger....
(sells more airplanes because they seem faster - same reason that $9.95 is better than $10 if you're selling somethign...)
Ahhh...the eternal question!
As a trained Aeronautical Engineer, it was beaten in to me that the REAL aviation world always does things in knots, and my papers would be failed if i used any other units...
As a Commercial and Instrument Pilot, I have been trained to do everything in knots, because that is what the ATC world uses.
In the Flight operations world in which I live, we do everything in knots because that is the engineering standard (see first bullet above...)
Many people like to use mph because the numbers are bigger....
(sells more airplanes because they seem faster - same reason that $9.95 is better than $10 if you're selling somethign...)
...Many people like to use mph because the numbers are bigger....
(sells more airplanes because they seem faster - same reason that $9.95 is better than $10 if you're selling somethign...)
ic... thanks
;-)
terrykohler
Well Known Member
RV-9A Speeds
If you look on this site for POH's, you'll see a listing for an RV9A. Look carefully at the listed speeds, and then disregard. I think it's an example of using cut and paste from an RV7 rather then generating numbers during flight testing.
That being said, the values I found for my 9A at gross weight were as follows:
Vx = 73 kts
Vy = 84 kts
Vs = 51 kts
Vso = 43 kts
In addition, I used the numbers given by Vans for Va (101 kts) and Vfe (78 kts). Also, you can see test numbers presented by www.cafefoundation.org
which all fall within a knot or two of those above. Their numbers are probably more accurate than mine (better equipment and training), but there is some variation from aircraft to aircraft.
Terry, CFI
RV-9A N323TP
If you look on this site for POH's, you'll see a listing for an RV9A. Look carefully at the listed speeds, and then disregard. I think it's an example of using cut and paste from an RV7 rather then generating numbers during flight testing.
That being said, the values I found for my 9A at gross weight were as follows:
Vx = 73 kts
Vy = 84 kts
Vs = 51 kts
Vso = 43 kts
In addition, I used the numbers given by Vans for Va (101 kts) and Vfe (78 kts). Also, you can see test numbers presented by www.cafefoundation.org
which all fall within a knot or two of those above. Their numbers are probably more accurate than mine (better equipment and training), but there is some variation from aircraft to aircraft.
Terry, CFI
RV-9A N323TP
Garage Guy
Well Known Member
Many people like to use mph because the numbers are bigger....
I've come to think that was the whole joke behind this thread too: http://www.vansairforce.com/community/showthread.php?t=46423
At 2700 RPM, torque in ft lbs is a bigger number than power in hp. So we like hp but we love torque! If Lycomings turned 5252 rpm, we would like them equally.
Back on topic, when we got our RV-6, the POH and placards on the panel had a mix of knots and mph. I've converted them all to knots now, just to reduce the cognitive load a bit. The steam ASI still has mph on the inner scale, in case I ever need to convert back...
--Paul
Flyfalcons
Well Known Member
Wang measuring.
Garage Guy
Well Known Member
Never been able to locate the knot line.
They are hiding as the minutes-of-longitude lines on your map.
--Paul
n5lp
fugio ergo sum
Well, latitude actually. The length of longitude minutes varies with latitude.They are hiding as the minutes-of-longitude lines on your map.
--Paul
Flyfalcons
Well Known Member
The vertical (longitude) minutes are constant.
Garage Guy
Well Known Member
Right you are. Should I now go back and edit my post and make it look like I know what I'm talking about? Nah...
--Paul
longranger
Well Known Member
Latitude is the angular displacement from equator, and is marked on the vertical scale on maps. Nominally, a minute of latitude is 1 nautical mile everywhere on the planet. Longitude is the angular displacment from the Greenwich Meridian, and is marked on the horizontal scale on maps. Nominally, 1 minute of longitude varies from 1 mile at the equator to zero at the poles.
Flyfalcons
Well Known Member
I believe you to be correct Longranger, I was reversing the mile marks on the longitude lines with longitude angles.
