#### Armilite

##### Well-Known Member

Ok, I have a friend who has a Kolb Firestar 2 which is tandem configuration, with a 503UL (50hp) with C Gear Box with a 3.0 to 1 ratio and a 71/72" Warp Drive Prop. 6500rpm / 3.0 = 2166.6 rpm for Prop. It's a (

A

He wants to put a 670 (

A 670 (More Weight & Cooling) with same

With a Take-off distance with a 503UL:

Empty weight:

Useful Load:

Stall speed: 30 kts (

Cruise speed: 61 kts (

VNE: 74 kts (

Climb: 800 ft/min (4.1 m/s)

Take-off distance:

Landing distance:

Fuel consumption:

Using Static Thrust Calc at 77F:

http://godolloairpor...c_eng/index.htm

**3**) Blade.A

**72" x 22**at 6500/3.0 = 2166.6rpm Pitched for**2066.6rpm**(**3**) Blade =**430.83**lbs needs**49.632**hp!He wants to put a 670 (

**93hp**) on it to increase his takeoff Performance for better Stol in the OutBack using the same 72" Prop & Grear Drive.A 670 (More Weight & Cooling) with same

**72"****x 41**at 6500/3.0 = 2166.6rpm Pitched for**2066.6rpm**(**3**) Blade =**430.83**lbs needs**92.496**hp!**A 72"****x 33**at 6500/3.0 = 2166.6rpm Pitched for**2066.6rpm**(**4**) Blade =**523.15**lbs needs**90.401**hp!With a Take-off distance with a 503UL:

**250 ft. Will you really Gain that much Shorter Takeoff Distance with the Higher 93hp Engine using the same 72" Length (3) Blade Prop or does he need a better prop?****Plane Specifications:**https://www.pilotmix.com/firestar-ii**MTOW:****725 lbs**(329 kg)**725 lbs**=**328.9 kg**/ 10kg =**32.8 kw**is needed =**43.98552 hp**(**44hp**) needed.Empty weight:

**325 lbs**(147 kg)**<---- A little Less since he took out the 2nd Seat.**Useful Load:

**400 lbs.**Stall speed: 30 kts (

**35 mph**) (56 kph)**<--- Can that be Improved! How much for a better Bush Plane?**Cruise speed: 61 kts (

**70 mph**) (113 kph)VNE: 74 kts (

**85 mph**) (137 kph)**<--- 503 50hp is probably pushing it close to the VNE.**Climb: 800 ft/min (4.1 m/s)

Take-off distance:

**250 ft**(76 m)Landing distance:

**300 ft**(91 m)**Engine: Rotax 503 (50hp)**Fuel consumption:

**4 GPH**(15.1 LPH)Using Static Thrust Calc at 77F:

http://godolloairpor...c_eng/index.htm

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