RV with 2-blade MTV-15
I was absolutely astonished! Never expected this.
---
a few years ago I bought your MTV-15-B/183-402 c/s metal prop for my RV. I would like you to know that the first flight happened on 9th April 2010, when after some three years of building and half a year pause, I was able to fly THE PLANE.
Well, it was a great moment for me, the one which I never forget. Now I have completed the testing and have 48 hrs on the Hobbs. Initially I thought I did not make a good choice with the prop as I could not get past 153 knots max speed at 8000 feet. (Van's performance data show 178 knots.) All the initial test flying (25 hrs ) was done without the undercarriage fairings and my RV friends kept on telling me that I would get some 12mph speed gain when fairings are fitted, but that I have to accept the c/s props do have a lower max speed as compared to fixed pitch Hertzel or Sensenitch props. The reason I selected your prop was that it had no restrictions through the whole range of speed. All the other prop did have one or the other restrictions in certain rpm ranges.
What I did like from the very beginning was a tremendous acceleration on the take off and a short take off run. Our airfield is at 3740 feet and temperatures in the summer do go up to 36deg C so we do experience density altitude above 6000 feet. Also, the braking effect of the prop on descent for landing and in the circuit is fantastic. I had a problem with screeching brakes from the very beginning and could not find any solution until recently.
Also I was testing the plane for shimmy on the undercarriage to find out if any wooden dampers would be required on the undercarriage legs (they are shown on the plans).
For those reasons I kept delaying fitting of the undercarriage fairings. Brakes sorted and no shimmy found, I was ready to fit the fairings. Opinions in local flying community as to what speed gain I will achieve vastly varied and nobody really new what fairing contributed by how much to drag reduction. So I decided to test it myself in order to find the real figures. I fitted each component/s and then test flew the plane at 8000 feet in NSEW legs of 15nm and measured the TAS by GPS. The results were:
Speed gain for individual fairings:
Main wheel fairings: 7 knots
Nose wheel fairing: 0 knots
Nose leg fairing: 5 knots
Main wheel legs + int. fairings: 10 knots
Main wheel legs + fuse int. fairings: 1 knots
==============================================
Total speed gain due to fairings: 23 knots
I was absolutely astonished! Never expected this. Well, the top speed of my RV is now 176 knots but I still have to adjust the prop governor to achieve engine speed of 2700rpm. At present the max revs are 2650 rpm.
Question to you is: Does efficiency of your prop go up with increased plane speed? Or what would be the reason for such a large speed gain as even comment from Ken Scott of Vans Aircraft was that he would have expected the gain to be about half of that I experienced. (The engine I am using is Superior XP-IO-360 with horizontal induction.) One more observation. During initial testing I was trying all three positions of flaps during a take off and on fully extended flaps, the plane would not accelerate past 85 knots. At our airfield the runway is 810m long and I normally do not use any flaps for take off even when fully loaded.
Passing the runway threshold (no wind) I normally get about 95 knots IAS. Well, I am very happy now that my choice of propeller based on your recommendation was correct and the performance of the prop / engine / plane combination has proven to be excellent!
Thanks for your advice and your product.
Best regards,
---
a few years ago I bought your MTV-15-B/183-402 c/s metal prop for my RV. I would like you to know that the first flight happened on 9th April 2010, when after some three years of building and half a year pause, I was able to fly THE PLANE.
Well, it was a great moment for me, the one which I never forget. Now I have completed the testing and have 48 hrs on the Hobbs. Initially I thought I did not make a good choice with the prop as I could not get past 153 knots max speed at 8000 feet. (Van's performance data show 178 knots.) All the initial test flying (25 hrs ) was done without the undercarriage fairings and my RV friends kept on telling me that I would get some 12mph speed gain when fairings are fitted, but that I have to accept the c/s props do have a lower max speed as compared to fixed pitch Hertzel or Sensenitch props. The reason I selected your prop was that it had no restrictions through the whole range of speed. All the other prop did have one or the other restrictions in certain rpm ranges.
What I did like from the very beginning was a tremendous acceleration on the take off and a short take off run. Our airfield is at 3740 feet and temperatures in the summer do go up to 36deg C so we do experience density altitude above 6000 feet. Also, the braking effect of the prop on descent for landing and in the circuit is fantastic. I had a problem with screeching brakes from the very beginning and could not find any solution until recently.
Also I was testing the plane for shimmy on the undercarriage to find out if any wooden dampers would be required on the undercarriage legs (they are shown on the plans).
For those reasons I kept delaying fitting of the undercarriage fairings. Brakes sorted and no shimmy found, I was ready to fit the fairings. Opinions in local flying community as to what speed gain I will achieve vastly varied and nobody really new what fairing contributed by how much to drag reduction. So I decided to test it myself in order to find the real figures. I fitted each component/s and then test flew the plane at 8000 feet in NSEW legs of 15nm and measured the TAS by GPS. The results were:
Speed gain for individual fairings:
Main wheel fairings: 7 knots
Nose wheel fairing: 0 knots
Nose leg fairing: 5 knots
Main wheel legs + int. fairings: 10 knots
Main wheel legs + fuse int. fairings: 1 knots
==============================================
Total speed gain due to fairings: 23 knots
I was absolutely astonished! Never expected this. Well, the top speed of my RV is now 176 knots but I still have to adjust the prop governor to achieve engine speed of 2700rpm. At present the max revs are 2650 rpm.
Question to you is: Does efficiency of your prop go up with increased plane speed? Or what would be the reason for such a large speed gain as even comment from Ken Scott of Vans Aircraft was that he would have expected the gain to be about half of that I experienced. (The engine I am using is Superior XP-IO-360 with horizontal induction.) One more observation. During initial testing I was trying all three positions of flaps during a take off and on fully extended flaps, the plane would not accelerate past 85 knots. At our airfield the runway is 810m long and I normally do not use any flaps for take off even when fully loaded.
Passing the runway threshold (no wind) I normally get about 95 knots IAS. Well, I am very happy now that my choice of propeller based on your recommendation was correct and the performance of the prop / engine / plane combination has proven to be excellent!
Thanks for your advice and your product.
Best regards,
Jaroslav
.png)
