HKS propeller testing and selection
Green Sky Adventures, Inc.    of North Central Florida
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Zippy Sport
Propeller Testing/Selection

Created Aug 14, 2003


Sept 30, 2003  Zippy Sport with HKS 700-E
The cowl construction is ready to test. 
Static run on Sept 29 indicates cooling is good, and there are no interference or rub points with the engine. Oil temp indicates less than 130F. Max observed CHT was 270F. EGTs were actually running lower than previous uncowled tests. At various cruise settings including decent, Mid 1300F was the observed high indicated temp.  Cruise speed of 100 mph + occurs at around 5,300 rpm.  Max rpm in straight and level flight is 6,000 with no appreciable gain in speed past about 5800. Max Speed is 114 mph
Prop is still the 60"tech III with 20 degrees of pitch (gsc pitch tool)
Oct 04, 2003 Zippy Sport with HKS 700-E
Fuel consumption test was performed today. With 5 gal of fuel in the main, forward tank, and the rear aux tank filled to the tippy top, Take off was performed on the main tank, with subsequent climb to 2500 feet.  With altitude and speed stable, one minute legs were flown, turning 90 degrees at the end of each leg.  Rpm was 5300 - 5400. Indicated airspeed was slightly over 100 mph.  GPS speed readings were between 98 and 106 mph, depending on direction of flight.  When the flight timer on the EIS turned 10 minutes, the fuel supply was switched to the rear tank, and the pattern, speed and altitude were maintained for 20 minutes. At that time, the fuel was switched back to the main tank for the remainder of this flight.  On the ground, it took 133 oz of fuel to top off the aux tank. Fuel burn calculation, then for the 100 mph cruise test is 3.12 gph.   ...  little over 32 miles per gal.
Oct 05, 2003 Zippy Sport with HKS 700-E
Washed the airplane and propeller. Installed the wheel pants over new 500x5 tires. Separate test flights were performed with each change.  Any speed increase was modest if at all.  Final test for the day, was to add prop pitch.  The decision was to go for 2 more degrees. 
With the prop set to 22 degrees pitch, rpm was limited to about 4700 on initial T/O run, but eventually came up to about 5000 as flying speed was attained.  At 2500 feet, full power level flight yielded 5740 rpm and 124 mph after one minute.  At 3000 feet, cruise speed of 115 was at 5500.  5300 was 107 or so.  There is a harmonic present between 4800 and 5160 that does not change with prop pitch. (this has also been noticed with various other Rotax engines with different combinations of propellers and gearboxes)  On the low side, 4400 maintained 70 to 75 mph.
Conclusion? We will probably remove 1 degree of pitch and see how that goes.
Oct 06, 2003 Zippy Sport with HKS 700-E
One more flight was made with the 60 tech III set at 22 degrees. Though TO and initial climb were not impressive, the easy 115 mph cruise was.  A cruise/climb test was initiated from full power, and 95 mph. Once established in the climb (no zoom climb) 600 feet per minute was the rate, between 2000 and 3000 feet.
Oct 06, 2003 Zippy Sport with HKS 700-E
Inspired by the good performance of the high pitch setting of the 60 tech III, more testing of Tech II 68 was in order, in search of better TO and climb.  The Tech II was set to 19 1/2 degrees of pitch, the static rpm was about the same as previous test, but rpm increased more rapidly as the aircraft would accelerate. This resulted in a better TO run and a better feeling departure climb in the 80 mph range.  MAX speed was 120 + at max level rpm of 5720.  Cruise at 5500 was 115. Also, in climb slowing the airspeed did not drag down the rpm as badly as the previous Tech III test. So, a good 80 mph climb speed was possible.  At lower rpm settings, 80 mph was very comfortable and steady at 4400 to 4500 rpm.

Note: this test was without the benefit of our 8 1/2" spinner. Oil temp was the highest observed thus far, 143 degrees.  The highest CHT was 290.

Oct 06, 2003 Zippy Sport with HKS 700-E
Our HOT ROD is  BACK!
Inspired by the slight improvement of the two blade over the three, testing of a shorter diameter higher pitched two blade was begun.  A 64 inch diameter Tech II was selected, and pitch was set at 21 degrees, or 58". As of this writing 10/07/03, an actual static test has not been performed, but Initial TO roll was about 5200.  Rpm was 5500 at the 65 mph rotation speed.  acceleration was brisk on TO, and the AC can once again, hang on the prop at 65 mph with a climb angle very reminiscent of the Rotax 582 installation.  Loss of daylight limited cruise test, but high power setting....upward of 6000 was showing 110..maybe 115.  Next will be to increase pitch, ...maybe one more degree.
July 2006 Zippy Sport with HKS-700e
The Zippy was the choice of rides for this years trip to Oshkosh. No changes had been made to the 64 inch Tech II set at 21 degrees, since last report nearly 3 years ago. The HKS has gained a little power since that time. TO rpm has been running about 5400.  In level flight rpm could easily exceed red line as the plain would accelerate. So, for the anticipated trip to Osh, a decision was made to sacrifice a bit of climb performance for higher cruise speed. Prop pitch was adjusted to 22 degrees resulting in a loss of about 200 rpm. By doing this, the max continuous rpm limit of 5800 was available for extra speed. The goal was 110 mph cruise, and this was achieved at 5600. Fuel burn during the 26 hours of flying averaged about 3.2 gph. We'll probably be trying some more combinations over the next little while.  
Sept. 2006 Kitfox II HKS- In anticipation of selling our Kitfox, we went back to the GSC tech II 68 which historically climbed the best for us. *This is still the case, but the vibration level, particularly in the 4000 - 5000 rpm range was annoying with this particular prop so it was back to the Ivo In-flight adjustable while the GSC prop gets rebalanced. However, at this time, the blades of the Ivo were shortened from the 70 inch diameter to 68.  One spacer was added to the low pitch stop. The high pitch stop was left alone. The thought being,  70 inch with 2.58 ratio was running a pretty flat pitch at TakeOff rpm. (6200)  and the last 2 inches may be more of a drag profile just going along for the ride. 
Back in the air, it's difficult to say if much has changed. Climb is 700 fpm at 817 lb takeoff weight at seal level. At max pitch in level flight, rpm tops out at 6000. with a little over 85 mph. 5800 rpm is good for about 80 and 70 mph at 5100.  Minimum cruise rpm is 4300 at about 55 mph. 
An interesting observation? At 70 mph and 5100 rpm with prop in max pitch, if the prop is flattened to minimum pitch, rpm goes up to 5800 and speed stays pretty much the same. So if this was configured as a ground adjustable prop, pitched for max performance takeoff, we'd be looking at a 70 mph cruise.
What effect on climb? Once established in a steady, full power climb at 60 mph, it really doesn't seem to make too much difference between climbing wide open throttle at 5600 rpm, or flattening the pitch for 6000. ...At least not according  to the VSI.  Where this may be more noticeable is take off. Acceleration to take off speed then best climb angle speed seems shorter with the rpm up.
Prop Pitch Aircraft Static RPM Prop RPM Date Density Alt
GSC Tech III 60 left 26 degrees
aprox 68" yes, 68" pitch, ..no misprint 
Zippy Sport 3820 1480 08/13/03 1800
GSC Tech II 68 left 13 degrees
37 ± inches
Zippy Sport 5840 2263 08/13/03 1800
*1 GSC Tech II 68 left
16 degrees
46 ±  inches
Zippy Sport
5520
2139
8/16/03
1900
*2 GSC Tech III 60 left
20 degrees
54" pitch
Zippy Sport
5100
1976
8/17/03
2100
GSC Tech III 60 left
20 degrees
54" pitch
"
5160
2000
9/29/03
700 est
GSC Tech III 60 left
22 degrees
58" pitch
"
4700
1821
10/05/03
1800
GSC Tech II
68 left
19 1/2 degrees
56" pitch
"
4700
1821
10/06/03
1800
GSC Tech II
64 left
21 degrees
58" pitch
"
5200
2015
10/06/03
1500
GSC Tech II
64 left
22 degrees
61" pitch
" 5200*3 2015 07/20/06 not recorded
Ivo 
70HP Left
14 degrees
at 8.5 frm tip
Kitfox II
5400
2093
12/08/04
700
Ivo 
70 in HP Left
13 degrees
at 8.5 frm tip
Kitfox II
5500
2132
12/13/04
300
GSC Tech II
68 left
15 degrees
Kitfox II
5200
2015
12/14/04
300
GSC Tech II
68 left
13 degrees
Kitfox II
5600
2170
12/15/04
400
Perry
71 x 37 left
37 inches
Kitfox II
5700
2209
12/18/04
300
GSC Tech II
68 left
12 degrees
Kitfox II
5800
2248
12/18/04
500
July 03, 2004 Thrust comparison Rotax 582 vs. HKS 700E
We were able to perform a head to head comparison thrust test today using two Summit powered parachutes. One with a Rotax 582 with 2.62 type E the other with an HKS 700-E 2.58 reduction. We were a little disappointed initially with the HKS Performance, that is, until we ran the 582. They ended up almost identical. ...Slightly over 300 lb for the HKS, and 305 for the Rotax. Density altitude at the time of the test was 3,200 feet. For the HKS to achieve the same performance (in static thrust) as the more powerful Rotax, a 64 inch GSC TECH III 3-blade prop was the choice. The 582 Summit uses a 60-inch.
December 08, 2004 Kitfox II installation
The HKS 700 E installation phase is complete on the Kitfox II. We're running a 70 inch 3 bld Ivo HP prop. At current setting of 14 degrees at 8 1/2 " from the tip, static rpm is 5400, yielding 700 fpm climb. We will be activating the in-flight adjustable capabilities of this shortly. It is believed that may make for some very good all around performance. During debugging and continued testing, we'll try to keep a chronology of those events here.
December 13, We dropped back another degree on pitch. The weather was a little cooler here this morning, around 50 degrees during the flight. Over the last few days, on numerous flights, sustained climb has been indicating between 700 and 800 fpm. Today's flight with about 5600 on climb had increased about 100 fpm.
December 14, A 68 GSC Tech II was tested at 15 degrees pitch. RPM was low 5K range. On a faster aircraft, this combination would probably be pretty good, but not for the KF II.   The next day, we dropped pitch back to 13 degrees. RPM was up to 5600 on take off, and performance was about the same as the original Ivo test. 
December 18, A 71 x 37 Perry prop was installed. RPM was about 5700 on take off and would hold 5800 in climb with a sustained rate of about 800 fpm through 3k feet. General performance was slightly better than the second Ivo test. 
December 18, The 68 Tech II was reinstalled, pitched to 12 degrees. Take off rpm was now 5800 and climb 6000.  Climb rate increased to almost 900 fpm. 
January 12, The 71 x 37 Perry was once again installed to check speeds. At 2500 feet msl and 5800 rpm our Kitfox is running 78 mph. At 5000 rpm, 68. Leveling the nose to accelerate just after liftoff allows the rpm to come up to 6000 fairly quickly, and climb rate at that power is about identical to high angle low speed climb. ...just a bit under 800 fpm OAT was in the mid seventies.
What have we learned?
Exactly what one might expect. The Kitfox is not fast. This one is a seventies something airplane. With encouragement, it will go faster, but it seems pretty happy stuck in the seventies. With steep pitched props loading the engine heavily, our plane goes a little faster for any given rpm. So theoretically, we could use a prop that limits rpm to 5800  (maximum allowable continuous) in level flight, and fly around at wide open throttle. That would be a condition that would provide the most encouragement to make the plane go fast. You could call it a cruise prop.  Every prop tested so far, flys our plane around nicely in the seventies. Take off and climb performance have increased with every increase in rpm. The 68 Tech II at 12 degrees was the first we've flown during this test series that allows rpm in excess of max allowable continuous in climb attitude. So while climbing out at 6000 rpm, we will have to reduce power to 5800 or less after 5 minutes. This has been the best climbing configuration tested to this point. Also, it is probably the slowest. 
How much slower?
December 20, 2004. We ran a gps speed check with the Tech II 68 set at 12 degrees. 5800 rpm at 1500 feet yielded 76 mph. Remember, in this configuration the engine is really unloaded. A short run of wide open throttle in level flight would run past the 6200 engine rpm limit.  On the slow side, it takes about 5000 rpm to maintain flight.  This testing is solo, with 8 gallons of fuel or less.  
Climb rate at altitude
December 22, 2004. Since our field elevation is only 158 ft. msl, our take off and climb performance is optimal. To explore climb capability that may exist on a hot summer day somewhere other than Florida, the following climb test was performed.
     "I went for some altitude climb numbers today on the GSC Tech II 68 at 12 
     degrees. Initial climb is pretty close to 900fpm. We could call it that if 
     fudge factor is considered. VSI is better than 8 most of the time and 
     occasionally 10.  RPM can be 6000, but I elected to run wide open throttle 
     with a little higher angle, which pulled rpm to 5800. With flaperon, climb 
     gradually diminished to about 500 + fpm at 5,000 feet. 

     At that point, I leveled off for a few minutes (Oil temp was still only up to 
     maybe 170, CHT a little over 300, but this is the highest I've seen it, and 
     I'm still testing heat proximity to gascolator and cowling.)
     On application of full power at 5k feet, 6000 rpm was max observed, but I 
     didn't let speed build, so it may have gone higher. I ran a climb angle that 
     held rpm around 5600 to 5800, initially searching for the best climb rate. 
     That was about 500 or a little over. 
     Now, I do have our HACman mixture control installed on this, but at this point 
     had only leaned very modestly because results to 5000 feet were not dramatic. 
     In this climb test after 5000 feet, I was shooting for 7500 to establish an 
     average rate. It held pretty close to 500, but gradually dropped off, as did 
     rpm. 
     Around 8000 feet, it would only hold about 5500 rpm at a high angle, maybe 300 
     rpm more at higher airspeed, but climb rate had diminished below 400 fpm. 
     While in climb, at high angle, holding 5500 rpm wide open throttle, I turned 
     out the HACman controller towards lean and observed an rpm increase of 300, 
     and climb increase of about 150 fpm. I repeated this from full rich to lean 
     several times, and the results were the same. This is not like  "war emergency" 
     power, but it is very dramatic."

*1 Time to climb test 8/17/03  10,000 feet.  average climb to 10,000 ft msl = 483 fpm
*2 To date, Aug 24, this has been the best combination for smoothness, TO, climb, and cruise.  Initially the max rpm was lower by approximately 100 rpm or more.  We are still running totally uncowled. Now, at 6  hours of operation, the engine has yet to consume 15 gallons of fuel.
*3 Power has increased slightly over the first approximately 50 hours. TO rpm had come up to 5400 with the 64 inch prop set at 21 degrees.