George,
Thanks for your insight...I'll make some inquiries regarding this prop that I have...
Couple of newby ops questions
Moderators: GAHorn, Karl Towle, Bruce Fenstermacher
Yes, Bill, there are issues with prop/engine/airframe combinations that may not first be apparent. Prop/engine combinations is a "black art" that involves (besides performance) vibration testing, to confirm during certification, how the combination affects both components. You'll notice for example, that some prop/engine/airframe combinations have rpm ranges that must be avoided for long periods of operation. This is due to a harmonic vibration that can lead to harmful effects on the crankshaft. Think of it like a pair of tuning forks, one the prop, the other the crank. They each have their own "note" when struck. Except they also have other harmonics because they may be "struck" at different frequencies (rpms) which may not be in "tune" with each other. Then these two tuning forks are bolted firmly together and must not have harmful effect upon one another. (Your brother and your sister each play two different instruments, one a trumpet and the other a french-horn...but they didn't bother to tune-up with each other using a common note and are out-of-tune... AND... they aren't playing the same piece of music. 
One is playing Sousa and the other Lohengrin. 
Your ears begin to bleed..... Your expensive, heirloom, leaded wine-glasses begin to shatter....
Moral: Be specific, don't trust prop shops to determine if your particular combination is correct. They are usually only concerned with the prop itself meeting it's mfr's specs, and may not concern themselves with what the customer intends to install it upon.
(Did your prop shop strike/mark the hub of the old prop (UnAirWorthy? and/or strike out the serial number? or model number?) They should have, which would help prevent an unsuspecting owner from installing it upon a certificated airplane.)
One is playing Sousa and the other Lohengrin. Your ears begin to bleed..... Your expensive, heirloom, leaded wine-glasses begin to shatter....
Moral: Be specific, don't trust prop shops to determine if your particular combination is correct. They are usually only concerned with the prop itself meeting it's mfr's specs, and may not concern themselves with what the customer intends to install it upon.
(Did your prop shop strike/mark the hub of the old prop (UnAirWorthy? and/or strike out the serial number? or model number?) They should have, which would help prevent an unsuspecting owner from installing it upon a certificated airplane.)
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
HOURS OR MINUTES
EVERYONE THINKS THERE ARE ONLY 60 MINUTES IN AN HOUR???? IF YOU ARE MOPING AROUND AT 2200RPM IT WILL TAKE MORE THAN "1 HOBBS" HOURS TO PUT AN INDICATED 1 HOUR ON YOUR TACH. (THAT IS WHY MANY OPERATORS PUT HOBBS METERS IN THE RENTAL FLEETS 
). IN ONE "CLOCK" HOUR YOU ARE ACTUALLY PUTTING LESS "TACH" HOURS AND WHICH "CLOCK" YOU USE WILL DETERMINE THE AMOUNT OF FUEL BURN YOU COME UP WITH.
STIRRING COLD OIL TAKES SOME TOLL ON THE AVAILABLE POWER SO LOW OIL TEMPS AND EXTREME COLD AIR FLOWING OVER THE CYLINDERS CAN CAUSE YOUR ENGINE TO USE SLIGHTLY MORE FUEL. DO YOU HAVE A CYL HEAD TEMP GAGE? THERE WAS A COLD WEATHER "KIT" SOLD BY CESSNA FOR THE EARLIER COWLS THAT LIMITED THE AMOUNT OF RAM AIR ALLOWED THROUGH THE ENGINE. THE "KIT" ALSO INCLUDED A COVER FOR THE ENGINE SUMP COOLING OPENING TO INCREASE TEMPS IN THE SUMP. PROBABLY HAD SOME VALIDITY IN OPERATIONS IN COLDER CLIMES.
AS OLE SHORTY FEEL FENSMACKER SEZ THIS IS WORTH ABOUT WHATCHER PAYIN FER IT
OLE GAR
). IN ONE "CLOCK" HOUR YOU ARE ACTUALLY PUTTING LESS "TACH" HOURS AND WHICH "CLOCK" YOU USE WILL DETERMINE THE AMOUNT OF FUEL BURN YOU COME UP WITH.STIRRING COLD OIL TAKES SOME TOLL ON THE AVAILABLE POWER SO LOW OIL TEMPS AND EXTREME COLD AIR FLOWING OVER THE CYLINDERS CAN CAUSE YOUR ENGINE TO USE SLIGHTLY MORE FUEL. DO YOU HAVE A CYL HEAD TEMP GAGE? THERE WAS A COLD WEATHER "KIT" SOLD BY CESSNA FOR THE EARLIER COWLS THAT LIMITED THE AMOUNT OF RAM AIR ALLOWED THROUGH THE ENGINE. THE "KIT" ALSO INCLUDED A COVER FOR THE ENGINE SUMP COOLING OPENING TO INCREASE TEMPS IN THE SUMP. PROBABLY HAD SOME VALIDITY IN OPERATIONS IN COLDER CLIMES.
AS OLE SHORTY FEEL FENSMACKER SEZ THIS IS WORTH ABOUT WHATCHER PAYIN FER IT
OLE GAROLE GAR SEZ - 4 Boats, 4 Planes, 4 houses. I've got to quit collecting!
Uhmm... If you are operating at lower rpms, relative to real time your tach is also recording lower engine hours,...and your fuel burn (in real time) is also lower (and in accordance with the performance charts which are using real time)... and Ol' Gar is right about which clock to use for flight planning versus flight recording. (He still smells fishy tho'.)
This would be a horse(power) of a different color as regards mpg vs economy. Sometimes it's better to burn the fuel at higher rpms to get to the destination sooner and spend less money on engine reserves.
An extreme example (for illustration) would be a 100 mph airplane flying into a 100 mph headwind. A fuel burn increase (by increasing power and therefore speed) would result in a lower cost per hour and lower cost per mile operation.
It's usually only economical to carry low power settings with a strong tailwind. Otherwise, recommended cruise (2450 with the standard setup) is optimal. On most trips I plan 10 gph the first hour, and 8 gph every hour afterwards, but usually beat it by a tenth of a gallon or so, which I disregard as a safety margin.
This would be a horse(power) of a different color as regards mpg vs economy. Sometimes it's better to burn the fuel at higher rpms to get to the destination sooner and spend less money on engine reserves.
An extreme example (for illustration) would be a 100 mph airplane flying into a 100 mph headwind. A fuel burn increase (by increasing power and therefore speed) would result in a lower cost per hour and lower cost per mile operation.
It's usually only economical to carry low power settings with a strong tailwind. Otherwise, recommended cruise (2450 with the standard setup) is optimal. On most trips I plan 10 gph the first hour, and 8 gph every hour afterwards, but usually beat it by a tenth of a gallon or so, which I disregard as a safety margin.
'53 B-model N146YS SN:25713
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.
50th Anniversary of Flight Model. Winner-Best Original 170B, 100th Anniversary of Flight Convention.
An originality nut (mostly) for the right reasons.