Mtns2Skies
Final Approach
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Mtns2Skies
Just a quick question on what exactly defines them as such and what advantages/disadvantages they have over a traditional prop?
Scimitar propeller
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Steve
En-Route
From Hartzell
The curved ScimitarPlus blades utilize a high lift series of airfoils at mid-blade sections to enhance aircraft take-off and climb performance. A combination of tip sweep and a series of airfoils at the tip sections cause lower transonic drag, resulting in a very low noise signature. This proprietary blend of airfoils also generates excellent cruise performance in the thinner air at high altitudes.
The curved ScimitarPlus blades utilize a high lift series of airfoils at mid-blade sections to enhance aircraft take-off and climb performance. A combination of tip sweep and a series of airfoils at the tip sections cause lower transonic drag, resulting in a very low noise signature. This proprietary blend of airfoils also generates excellent cruise performance in the thinner air at high altitudes.
Mtns2Skies
Final Approach
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So that means the scimitar blade has better climb performance than even just the transition to a 3 bladed prop?
Dan Thomas
Touchdown! Greaser!
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Dan Thomas
There was a scimitar prop made for homebuilders years ago that had some constant-speed properties. The curved blades twisted to a lower pitch at higher blade AoAs to allow better RPM at takeoff and in the climb, and as the AoA decreased when speed built they would flex back to a higher pitch. The change wasn't big but was better than nothing. Wooden, they were, but I suppose a composite prop could do it, too.
I don't think an aluminum prop could do it as well. In fact, much curve introduces more stress in the trailing edge and could lead to cracking. The "gullwing" McCauley props used on the Cessna 152 had cracking issues at the bends near the hub. Centrifugal forces try to straighten the bend and end up cracking it.
Dan
I don't think an aluminum prop could do it as well. In fact, much curve introduces more stress in the trailing edge and could lead to cracking. The "gullwing" McCauley props used on the Cessna 152 had cracking issues at the bends near the hub. Centrifugal forces try to straighten the bend and end up cracking it.
Dan
BiffJ
Pre-takeoff checklist
The shape of the blade is what determines the designation as Scimitar. As for the performance gains or losses its more related to the design of the particular blade than just the shape. The shape has been used on many different props over time and some were better, some worse. You will have to get info on the specific prop rather than just the shape to get any real useful info. I don't have direct experience flying any of the new Hartzell's but friends who have flown them claim they are quieter and pull as well if not better than what they were flying previously.
The idea that a 3 bladed prop adds to climb performance is also not too accurate. The adding of blades is normally done to decrease the load per blade for either noise reasons or horsepower . It is done to prevent the prop from becoming too large in diameter when the power is high and ground clearance low or if the amount of power requires blades of a length that would create transonic losses at the tips. Cessna 185's were a very good example of this when they went to the 310HP engines. They put the 3 bladed prop on because the 2 blader made so much noise and lost a lot of efficiency because it had to be so long that the tips were breaking the speed of sound at take off rpm. Think of the T-6's you've heard....they have a very noisy prop on take off. So the point of this is to show that while some props may have features like better climb or faster cruise, its not just the shape or number of blades that make them that way.
Your best info on the Scimitar Hartzells will come from Hartzell themselves. Have a look at their website.
Frank
The idea that a 3 bladed prop adds to climb performance is also not too accurate. The adding of blades is normally done to decrease the load per blade for either noise reasons or horsepower . It is done to prevent the prop from becoming too large in diameter when the power is high and ground clearance low or if the amount of power requires blades of a length that would create transonic losses at the tips. Cessna 185's were a very good example of this when they went to the 310HP engines. They put the 3 bladed prop on because the 2 blader made so much noise and lost a lot of efficiency because it had to be so long that the tips were breaking the speed of sound at take off rpm. Think of the T-6's you've heard....they have a very noisy prop on take off. So the point of this is to show that while some props may have features like better climb or faster cruise, its not just the shape or number of blades that make them that way.
Your best info on the Scimitar Hartzells will come from Hartzell themselves. Have a look at their website.
Frank
EvilEagle
Pattern Altitude
I just got one. It's a Prince P-Tip and they make it in wood or wood with carbon overlay.