[stneki]

During my recent proficiency review my CFI asked for a takeoff and landing runway requirements with 50 foot obstacle clearance, no wind, 90 degree day and 1800 feet density altitude. This would be on asphalt.

My plane is an RV7A with 180 HP and fixed pitch prop.

I have no idea. Does anybody have any data to determine this?

Thanks Steve
Dues Paid
N315S

 

[turbo]

My guess is probably about 1400'. Because there is no POH you are on your own to figure it out.

 

[Sid Lambert]

Did you ask if you just go around it?

 

[flyboy1963]

No idea....a fair statement

I think this is a serious issue! How many of us have all the flight test data from phase 1, but really don't have nearly enough to make performance tables that are useful.
I mean, pretty tough to find an airport that would allow you to have a bunch of guys wandering around the runway with chalk and tape measures to allow us to measure these exact parameters!???

has anyone been able to do this?...and would their data be useful, or misleading if we used it for another of same model etc.?

 

[Ironflight]

has anyone been able to do this?...and would their data be useful, or misleading if we used it for another of same model etc.?

When I tested my -8, I had a group of Aero Engineering Students who were cooping and interning for us get involved and they helped me with runway lengths for takeoff and landing. It is not simple, as you suspect, and the data basically showed that if I had 1,000', I could always get in and out. Pilot attention to details was the biggest variation. My numbers are all buried in packed boxes.

 

[Bob Redman]

PERFORMANCE FACTORS

G'day Steve,

Determining complete take-off & landing performance data for each experimental aircraft takes considerable time & resources.

Van has published distance required to clear a 50ft obstacle for RV-7/7A (& other models - see factory website) fitted with a Hartzell constant speed prop which does not help you much, but did help me, and may help others with the same prop.

I confirmed the Van data at 1400 and 1800lb assuming standard ICAO atmosphere (15degC, 59degF and sea level) and added my own pessimism (say add 10%) and then use take-off and landing performance factors published by the UK Civil Aviation Authority to help estimate distance required for various conditions.

I know I am OK flying to/from strips up to 3000ft length and 3K density altitude but start looking more closely at the factors for shorter strips and higher DA's.

I have tried attaching the table to this post but failed. I will e-mail it to Doug Reeves and hopefully he will add it.

As you have a fixed pitch prop you may have to measure your take-off and landing distance using two or three friends and a distance measuring wheel to gather the base data for, say, 1400 and 1800lb. You will have to decide yourself how much data you need for your manner of operating and your tolerance for risk.

Good luck and regards,

 

[hevansrv7a]

Half-vast approach?

During my recent proficiency review my CFI asked for a takeoff and landing runway requirements with 50 foot obstacle clearance, no wind, 90 degree day and 1800 feet density altitude. This would be on asphalt.

My plane is an RV7A with 180 HP and fixed pitch prop.

I have no idea. Does anybody have any data to determine this?

Thanks Steve
Dues Paid
N315S

This might be good enough for "government work".
1. Determine your best short take-off technique to leave ground effect.
2. Determine your best-angle AOA or IAS. AOA is the better way if available. This is much easier with an EFIS that shows not just pitch but a pointer that shows where the airplane is going (GRT does this) because otherwise there is a lot of math involved. Best rate is not the same. Or is it?
3. In my experience, the FP prop leaves me with the same IAS for best angle and best rate. This is not what most expect but it is true for my plane.
4. Assuming a good EFIS with WAAS-GPS, do the maximum performance take off and climb while recording position and speed. Later you can determine from the recorded data where you were when your altitude gain was 51'.
5. Repeat #4 at a few temperature and weight points and draw the curves.

 

[hydroguy2]

Our EAA chapter or maybe it was the MPA, set up a theodolite. We used Townsend airport (8U8) and marked off 200' stripes using the football field chalk machine. The station was set up about 1500' down the strip, then after people calculated their distance(which the wrote down) we positioned them to cross the station at 50' AGL. If you crossed us less than 50' you got a DNF because you hit the obstacle. Also had a landing distance check, where you had to tell them where you could be stopped by....and could not land before the chalk box. Had 1 guy complain because he easily made the taxiway turnoff....but he landed 50' short of the zone hitting the theoretical cliff.

Many failures on both checks. Lots of fun though.

 

[Don]

Our EAA chapter or maybe it was the MPA, set up a theodolite. We used Townsend airport (8U8) and marked off 200' stripes using the football field chalk machine. The station was set up about 1500' down the strip, then after people calculated their distance(which the wrote down) we positioned them to cross the station at 50' AGL. If you crossed us less than 50' you got a DNF because you hit the obstacle. Also had a landing distance check, where you had to tell them where you could be stopped by....and could not land before the chalk box. Had 1 guy complain because he easily made the taxiway turnoff....but he landed 50' short of the zone hitting the theoretical cliff.

Many failures on both checks. Lots of fun though.

I have heard it said (and repeated it myself) theory and practice and only the same in theory. Supposedly Yogi Berra said it first. In any event, this is a classic example and would make a great practice session for pilots trying to see what their plane can do. I will propose this at my next meeting....and if it goes like all of my other suggestions over the past 14 years, I will find.a new chapter who might be receptive to an interesting and useful idea.

 

[TomVal]

Takeoff distance calculation...

In the U.S. an easy way to estimate takeoff distance is to use the runway edge lights for reference. If the runway has a STANDARD lighting configuration (check with the airport manager), runway edge lights are spaced every 200 feet. During your takeoff runs, have an outside observer note your liftoff point, count the number of edge lights to your liftoff point and then do the math (interpolate as required).

As far as takeoff distance at 50 feet AGL, use Rate of Climb at Vx and do the math to 50 feet AGL. For example, with a 500 feet ROC, the aircraft would be at 50 feet AGL in 6 seconds. At wheel liftoff the observer could use a countdown timer or a manual count to 6 seconds, note the distance in reference to the runway edge lights, then do the math

Not exactly scientific, but it could at least give you a ballpark estimate of your takeoff distance.

In the old days at Cessna, we used a high speed camera in a fixed position abeam the runway and a set of calipers to generate the performance numbers that got published in the POH.

 

[gasman]

Numbers in your POH are fine, and should be there. But the fact is, if an RV (don't know about the 12) can't make it in or out of an airstrip with a 50 foot obstacle, then the airstrip is useless to 99.9% of GA aircraft.

Here is one such runway W/O a 50 foot obstacle...... http://www.airport-data.com/airport/6MO1/#location

Of course, it takes way more skill to land short field over a 50 foot obstacle than to blast out over it..

Question???? How close does the 50 foot obstacle need to be to the approach end of the runway to make it an obstacle?

 

[paul330]

Question???? How close does the 50 foot obstacle need to be to the approach end of the runway to make it an obstacle?

Good question.

Assume you need to clear an obstacle by 50', then you are looking at where your height is 100' aal on approach. On a 3 deg approach, that would be about 600' from your aim point.

Of course, you could happily fly a steeper approach in an RV. At London City Airport, they certified approaches of 5 deg - for noise rather than obstacles, I believe.

 

[AirbusPilot]

Use XAVION app

Hi,

I am using Xavion app to measure takeoff distance to 50 ft, in my case (RV-8) it is around 1000 feet.

I hope this help,

Fernando

 

[stneki]

Thank you to the group for the help. I will try some of the suggestions and put some buddies to work.

Steve
RV7A
N315S