Best Approach Speed?

Best Approach Speed for RV-10

Anybody have any suggestions on the best approach speed for the RV-10?

How does it compare to the RV-9 in terms of handling for a low time pilot?

Each aircraft will have its own static system position errors, and each ASI will have its own instrument error. So, if you flew two aircraft in close formation, so they were at the same airspeed, the ASIs would read different values. There could easily be 10 kt difference in indicated airspeeds at the same calibrated airspeed.

The indicated airspeed that is perfect for approach on one RV with one pilot at one airport may be all wrong for you, your RV and your airport.

I suggest a careful series of approach and landing flight tests in smooth air, at max landing weight and forward CG, reducing the approach speed by a knot or two for each approach. Find the slowest speed at which you can get an acceptable flare and touchdown. Add 5 kts to allow a bit of margin, and this becomes your minimum approach speed in smooth air. Add a bit more speed if the air is turbulent.

Kevin, thanks for the reply. Good points about the innacuracies in different indicators. I wasn't really considering those factors. I was thinking more of a ballpark target figure to use as a starting point.

I've read that a good rule of thumb is 1.3 times the stall speed. According to Van's published figures, the stall speed for the RV-10 is 57 mph (~50 knots) at light weight, and 63 mph (~55 knots) at gross weight. The 1.3x rule of thumb would give target approach speeds of 65 knots at light weight and 72 knots at gross weight.

65 knots is my target approach speed in the Cessna Skyhawk that I'm training in right now, which seems pretty docile and easy to control. I've come in at 72 knots before and didn't have too much trouble, just required a longer landing distance. So using that as a comparison, it seems like the RV-10 is pretty docile, despite it's more powerful engine.

FWIW, I completed my first solo this morning at DuPage Airport (KDPA). Woo hoo!!!

Roadster said:

I've read that a good rule of thumb is 1.3 times the stall speed. According to Van's published figures, the stall speed for the RV-10 is 57 mph (~50 knots) at light weight, and 63 mph (~55 knots) at gross weight. The 1.3x rule of thumb would give target approach speeds of 65 knots at light weight and 72 knots at gross weight.

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1.3 times the stall speed is used on a lot of larger aircraft. There are two things to keep in mind:

1. The margin of 30% between the stall speed and the approach speed represents quite a few knots if the aircraft has a high stall speed, as with airliners. But, it is only a few knots on slower aircraft. A 30% margin might not be enough on some aircraft.

2. That 30% margin is intended to be a margin of 30% calibrated airspeed, not indicated stall speed. Many aircraft have airspeed systems with very large errors at slow speed, so if you simply multiply the IAS at the stall by 1.3 you might have an approach speed that is quite slow. For example, I sometimes fly a C182Q. The POH shows a stall speed of 45 kt indicated airspeed, or 54 kt calibrated stalls speed, with landing flap, at max weight and forward CG - in other words the ASI is reading 9 kt too slow at the stall, and that assumes no instrument error. In reality, the one I fly indicates about 40 kt at the stall under these conditions, so I think there is some instrument error too.

If I simply multiply 45 kt IAS times 1.3, I get 58.5 kt. The airspeed calibration chart says that 58.5 IAS would be about 61 kt CAS. If the stall is 54 kt CAS, 61 kt CAS is only about 13% above the stall. I've done approaches at 60 kt IAS on this aircraft, and there isn't any margin for a gust, or a pilot error. This is too slow for a normal approach speed, on this aircraft. 1.3 times the actual indicated stall speed of 40 kt wouldn't leave enough airspeed to flare, in my opinion.

Bottom line - don't put too much stock in the 1.3 times stall speed rule of thumb, unless your flight testing shows that it works for your aircraft.

Roadster said:

FWIW, I completed my first solo this morning at DuPage Airport (KDPA). Woo hoo!!!

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Congratulations! Way to go.

Angle of attack indicator

Kevin, I noticed you do not have a dedicated AOA instrument in your panel yet. Are you planning to add one, or just use the Dynon? It seems like a good angle of attack indicator, properly calibrated, would be a good way to set the approach speed.

Mickey,

If I was planning to operate from a very short strip, so that I needed to get the max performance from the aircraft, I would add an AOA system, so I could fly the optimum approach speed on every approach. But, I'll be flying from strips long enough that I can afford to simply base my approach speed on the ASI, and accept that I might be flying a bit faster than necessary if lighter than max weight.

If after I get flying, I find that my -8 doesn't have the pre-stall buffet that many -8s do, then I'll be looking for a way to achieve stall warning. I might get that with stall strips on the wing LE. If that doesn't work, I'll add an AOA system with an aural stall warning.

I'm not doing any more panel mods now, as I need to get flying.

Seager uses 90 mph (80 knots) indicated

Kevin Horton said:

1.3 times the stall speed is used on a lot of larger aircraft. There are two things to keep in mind:

1. The margin of 30% between the stall speed and the approach speed represents quite a few knots if the aircraft has a high stall speed, as with airliners. But, it is only a few knots on slower aircraft. A 30% margin might not be enough on some aircraft.

2. That 30% margin is intended to be a margin of 30% calibrated airspeed, not indicated stall speed. Many aircraft have airspeed systems with very large errors at slow speed, so if you simply multiply the IAS at the stall by 1.3 you might have an approach speed that is quite slow. For example, I sometimes fly a C182Q. The POH shows a stall speed of 45 kt indicated airspeed, or 54 kt calibrated stalls speed, with landing flap, at max weight and forward CG - in other words the ASI is reading 9 kt too slow at the stall, and that assumes no instrument error. In reality, the one I fly indicates about 40 kt at the stall under these conditions, so I think there is some instrument error too.

If I simply multiply 45 kt IAS times 1.3, I get 58.5 kt. The airspeed calibration chart says that 58.5 IAS would be about 61 kt CAS. If the stall is 54 kt CAS, 61 kt CAS is only about 13% above the stall. I've done approaches at 60 kt IAS on this aircraft, and there isn't any margin for a gust, or a pilot error. This is too slow for a normal approach speed, on this aircraft. 1.3 times the actual indicated stall speed of 40 kt wouldn't leave enough airspeed to flare, in my opinion.

Bottom line - don't put too much stock in the 1.3 times stall speed rule of thumb, unless your flight testing shows that it works for your aircraft.

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Congratulations! Way to go.

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Kevin, thanks for the detailed explanation, and for the congratulations. I completed my night flight requirements a few weeks ago. Getting close.

I took a demo ride with Mike Seager this weekend, and he told me his target approach speed in Van's RV-10 is 90 mph indicated (80 knots). That's exactly what he used when landing the demo ride, and it was a nice, smooth landing.

Very impressive aircraft! Empennage kit arrives in a couple of weeks.

RV-10 Approach Speed

All of you should listen to Mike S as he has more time than any of us most likely. However, I target 85 mph on final with full flaps. I find 90 is a little too fast. This speed seems to work at all weights.
Vic

"left wing heavy"

vic syracuse said:

All of you should listen to Mike S as he has more time than any of us most likely. However, I target 85 mph on final with full flaps. I find 90 is a little too fast. This speed seems to work at all weights.
Vic

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Vic, thanks for your feedback.

I was just reading your first flight report, and I noticed one of your initial squawks stated "left wing heavy and it needs right rudder trim in cruise".

http://www.vansairforce.com/community/showpost.php?p=12836&postcount=2

Did you ever get that problem sorted out, and if so, what did you do to correct it?

Induced Drag

Another consideration, besides all the excellent gen from Kevin, is the very low aspect ratio of RV aircraft compared to most manufactured aeroplanes.
The low aspect ratio wing can develop significant induced drag in the flare. If you strike undershoot windshear (that is a big decrease in wind) just before or during the flare the resulting need to apply significant back stick to increase the angle of attack to compensate for the airspeed loss can result in a large and sudden airspeed loss. Hence the need to be very aware of possible windshear and the need to consider carrying a few extra knots to protect against this.
Also significant is that at approach speed in an RV you are well into the back of the drag curve already, so any decrease of airspeed on final increases drag and will tend to cause a further decrease in airspeed.
Any clarification welcome Kevin.

Pete.

Yep...

Yepper, Fod hit it right on the nose in technical terms. I am 100% in agreement with him.....
Here is what I teach/tell/recommend to all I am with that flies 331JH, based on my 130+ hours in Jim's plane.......
****No flap/engine out...100 mph untill landing assure, then flaps as desired. NOTE, it is a significant nose low attitude with CS prop at this A/S, and even more so when full flaps are selected! Beware of RV sink! Yep, even the 10 has quite a bit of RV sink, albiet not as bad as say a 6.
**** Normal landing.... min of 100 on downwind, approaching base, apply desired flaps. Now, since with a fwd CG, full flaps results in requiring the holding of aft stick pressure, I teach to apply only as much flaps as one can apply and be able to trim off stick pressures. For me, this is about half flaps solo to 3/4 flaps fully loaded. ( at extreme aft envelope CG's, one is able to select full flaps and trim hands off).
****Base to final, min 90mph.
**** Final, 85 min, max of 90.
**** Cross fence as low as 80...bare minimum!!!.
**** I caution all to at least PLAN to carry power through the flare, due to bare minimum elev. authority at touchdown speeds.
****I ALWAYS caution EVERY new RV driver, and the 10 is no exception. (proven on test flights)...That if engine fails on final ESPECIALLY if flaps are selected, one must IMMEDIATELY and rapidly lower the nose (much worse on CS planes) to prevent an extremely high sink rate/landing/crash short of the runway! Of course this becomes more evident/necessary the more power that is carried on final.
Hope this helps, and I would like comments/critiques from any other experienced 10 drivers.
Glen