Rear Bear Vs. The Russian Bear

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bmcj

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Rare Bear vs Tupolev Bear.

You're comparing piston to turboprop!

By the way, it's Rare Bear, not Rear Bear (or Bare Rear :gig:).

... or near beer?
 

bmcj

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Maybe so, but the Rare Bear speeds are at (or near) sea level and include lots of speed-robbing turns.
 

pie_row

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Maybe so, but the Rare Bear speeds are at (or near) sea level and include lots of speed-robbing turns.

The Tu=95 holds the propeller speed record for it's weight class at at 507 mph over a closed corce of 1,000km. FAI certifide record. I looked for the referance that quoted 996 kmph and didn't find it so I won't repeat it.
 

autoreply

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If you're comparing equivalent drag area and horsepower the TU-95 tops out the Bearcat. That's the slender fuselage, very powerful engines, swept wing, but also the sheer power sensity of turboprops you simply can't achieve with reciprocating engines.
 

bmcj

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Good points, how about apples to apples, how fast will/would/has/can a TU95 go at sea level? What's the straight line top speed of the Bare Bear?
I don't know any of those off the top of my head, but remember, TAS (true airspeed) is much greater than IAS (indicated airspeed) at high altitudes, while the speed of sound is slower. This means that your speed in terms of Mach number will be higher at altitude.
 

Starman

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To make it a better race, assuming the Rare Bear has a supercharger, find it's fastest altitude and then find the top speed of the TU95 at that altitude. It should be easy for the rocket scientists here.
 

bmcj

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Just to give you an example, a plane flying at .8 Mach at 5,000 feet (Rare Bear) will indicate 480 knots with a true airspeed of 515 knots. A plane flying at .8 Mach at 40,000 feet (Tupolev Bear) will indicate 240 knots with a true airspeed of 455 knots. The difference in true airspeeds at various altitudes is why planes fly higher to cover more real estate faster.

Also, comparing the Mach number of two means nothing unless it is done under the same conditions (altitude, pressure, temperature). For example, our plane flying at Mach .8 at 5,000 feet will cover ground 5 knots faster than a plane flying at Mach .9 at 40,000 feet. Despite being at a higher Mach number, the speed of sound is slower, and so is the true airspeed.

NOTE: These numbers are taken from a chart and are not exact.
 

Starman

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For example, our plane flying at Mach .8 at 5,000 feet will cover ground 5 knots faster than a plane flying at Mach .9 at 40,000 feet.
And there you have it folks, the Rare Bear beats the Tu by a landslide and following mach numbers is like chasing ghosts.
 
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autoreply

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To make it a better race, assuming the Rare Bear has a supercharger, find it's fastest altitude and then find the top speed of the TU95 at that altitude. It should be easy for the rocket scientists here.
In fact, with constant pressurization (ratios) top speed at all levels for both a turboprop and reciprocating engine is almost constant :)
 

autoreply

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I've taken a good hard look at the power density that you can achieve with piston engines. Done right on a per lb bases you can make a piston engine that has a higher power density.
No, you won't.
The lightest engines are motorcycle ones. The 190HP 1000CC engines weight about 85kg. So exactly 1 lbs/hp.
The PT-6 does around 1200HP and 300 kg, so 0.5 lbs/hp.

Not to mention that I'm comparing a pure racing engine without gearbox with the most reliable turboprop in the world.
 

bmcj

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Autoreply is correct. In fact, the power output is largely a function of how much fuel you can put through it. The turbines win that race hands down for a given engine weight.
 

Autodidact

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I hate to keep hollering Reynolds number, but might that have something to do with it? The TU-95 is a much larger airplane than the Bearcat. In naval architecture, a ship with a displacement type hull will have a higher hull speed the longer it is because it can only go the speed of a wave whose distance between crests is the same as the distance between the bow wave and the stern wave of the hull. It can go faster, but the efficiency goes way down. I realize that water and air are not exactly the same, but it does seem that the fastest aircraft tend to be fairly large. Missiles are probably the fastest but they are seriously overpowered. Any correlation between size and speed?:ermm:
 

Starman

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For example, our plane flying at Mach .8 at 5,000 feet will cover ground 5 knots faster than a plane flying at Mach .9 at 40,000 feet.
And there you have it folks, the Rare Bear beats the Tu by a landslide and following mach numbers is like chasing ghosts.
Or maybe not, at lower altitudes the TU will have more advantageous prop blade angles and more air for more engine power so maybe it could really crank it on and beat the Rear bare at lower altitudes, you would need to know if and/or how much the TU engines loose power at high cruise altitude.
 

Topaz

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Are we really comparing a high-altitude four-engine bomber with a low-level closed-course racer just because they both have propellers? This isn't even apples-to-oranges. More like apples-to-aardvarks.
 
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