Greetings,
Please confirm the differences between the C172R & S (aka SP) are:
1.) Increase of HP from 160 to 180 with the same Lycoming engine;
2.) A more efficient prop pitch permitting an increase in HP & RPM (2700);
3.) An increase MGTOW from 2450 to 2550 pounds.
In another post (that I am unable to locate now), a gentlemen provides an excellent explanation of all this explaining that A2A has actually provided two aircraft (C172R & SP) in one. Not surprisingly, I prefer the upgrade and I know all this is well documented within A2A and externally.
Are there other readings and/or comments?
Thanks in advance / Les Parson
C172R & C172SP
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- Staff Sergeant
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- Technical Sergeant
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Re: C172R & C172SP
Yes for all. About "more efficient", dunno, S prop has a finer pitch, so it revs more, but R might be more economic at cruise (or not, dunno).Les Parson wrote:Greetings,
Please confirm the differences between the C172R & S (aka SP) are:
1.) Increase of HP from 160 to 180 with the same Lycoming engine;
2.) A more efficient prop pitch permitting an increase in HP & RPM (2700);
3.) An increase MGTOW from 2450 to 2550 pounds.
In another post (that I am unable to locate now), a gentlemen provides an excellent explanation of all this explaining that A2A has actually provided two aircraft (C172R & SP) in one. Not surprisingly, I prefer the upgrade and I know all this is well documented within A2A and externally.
And yes, in practice, you have two different planes, but with 2700rpm S prop you should have different air speed indicator :Q Another than that you basicly have R and S versions of the 172.....
Re: C172R & C172SP
Hi Les,
Yes that's about it. From technical point of view, in real life the 172R model may be 'upgraded', if you will, to 172S weights by incorporating a modification no. MK172-72-01. The main difference is that the McCauley 1C235/LFA7570 (to be exact! ) propeller is replaced with 1A170E/JHA7660.
About the slight misconception about the propeller efficiency. Generally, when some planes are equipped with finer pitch, higher rpm props, they are often referred to as "climb propellers", and the lower rpm props as "cruise propellers". That tells the difference, pretty much. You achieve much better climb rates with higher rpm propeller. At the same specific cruise rpm setting, though, the 172R with it's default propeller actually cruises a bit faster. If you think about it, it's all obvious.
However, it also seems to go unnoticed that there are a few other minor differences that you need to realize in real life. The basic R model uses 4-ply rated main tires, while the S, or modified R, requires 6-ply. Moreover, the correct nose wheel pressure for default R is 34 psi while the modded or the S model needs 45 psi.
-Esa
Yes that's about it. From technical point of view, in real life the 172R model may be 'upgraded', if you will, to 172S weights by incorporating a modification no. MK172-72-01. The main difference is that the McCauley 1C235/LFA7570 (to be exact! ) propeller is replaced with 1A170E/JHA7660.
About the slight misconception about the propeller efficiency. Generally, when some planes are equipped with finer pitch, higher rpm props, they are often referred to as "climb propellers", and the lower rpm props as "cruise propellers". That tells the difference, pretty much. You achieve much better climb rates with higher rpm propeller. At the same specific cruise rpm setting, though, the 172R with it's default propeller actually cruises a bit faster. If you think about it, it's all obvious.
However, it also seems to go unnoticed that there are a few other minor differences that you need to realize in real life. The basic R model uses 4-ply rated main tires, while the S, or modified R, requires 6-ply. Moreover, the correct nose wheel pressure for default R is 34 psi while the modded or the S model needs 45 psi.
-Esa
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Re: C172R & C172SP
Thanks for all the valuable information. Are there really any ASI differences? I wouldn't think so as there really aren't any airframe mods that I can see.
- Great Ozzie
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Re: C172R & C172SP
Higher Vso and Vs1 due to the increase in gross weight.Les Parson wrote:Thanks for all the valuable information. Are there really any ASI differences? I wouldn't think so as there really aren't any airframe mods that I can see.
Rob Osborne
Flight Instructor - CFI, CFII, MEI, MEII
A & P Mechanic
FAASTeam - Safer Skies Through Education
Professionalism in aviation is the pursuit of excellence through discipline, ethical behavior and continuous improvement. NBAA
Flight Instructor - CFI, CFII, MEI, MEII
A & P Mechanic
FAASTeam - Safer Skies Through Education
Professionalism in aviation is the pursuit of excellence through discipline, ethical behavior and continuous improvement. NBAA
Re: C172R & C172SP
Les,
Yes, the real life 172R does have a different airspeed indicator than the 172S or an R model modified to S specification. I don't have any picture at hand, or in memory, but the difference in air speed limitations is the maneuvering speed: 99 / 105 kIAS for R model / S and modified R model respectively. I'm not sure if there are other differences in the indicator face.
There also seems to be minor changes to allowable baggage limitations (defined as 120 lbs at 95'' aft for R model; 120 lbs at between 82''-108'' aft and 50 lbs at between 108''-142'' aft with combined maximum of 120 lbs for modified R and S models - I don't know why), lower usable engine oil quantity of 3.0 quarts against 3.5 in unmodified, again - don't know why, etc.
To correct my self a bit, it seems that the Cessna modification that I mentioned is only eligible for very few S/N's, so it probably just means the factory produced aircraft under 172R designation but produced to 172S specification. I'm quite sure though that I remember there is an equivalent STC out there available to other 172R planes.
Edit: probably as above!
-Esa
Yes, the real life 172R does have a different airspeed indicator than the 172S or an R model modified to S specification. I don't have any picture at hand, or in memory, but the difference in air speed limitations is the maneuvering speed: 99 / 105 kIAS for R model / S and modified R model respectively. I'm not sure if there are other differences in the indicator face.
There also seems to be minor changes to allowable baggage limitations (defined as 120 lbs at 95'' aft for R model; 120 lbs at between 82''-108'' aft and 50 lbs at between 108''-142'' aft with combined maximum of 120 lbs for modified R and S models - I don't know why), lower usable engine oil quantity of 3.0 quarts against 3.5 in unmodified, again - don't know why, etc.
To correct my self a bit, it seems that the Cessna modification that I mentioned is only eligible for very few S/N's, so it probably just means the factory produced aircraft under 172R designation but produced to 172S specification. I'm quite sure though that I remember there is an equivalent STC out there available to other 172R planes.
Edit: probably as above!
-Esa
- Great Ozzie
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Re: C172R & C172SP
Well, there will have to be for the changes in Vso & Vs1.AKar wrote:I'm not sure if there are other differences in the indicator face.
Va is not on the ASI.
Rob Osborne
Flight Instructor - CFI, CFII, MEI, MEII
A & P Mechanic
FAASTeam - Safer Skies Through Education
Professionalism in aviation is the pursuit of excellence through discipline, ethical behavior and continuous improvement. NBAA
Flight Instructor - CFI, CFII, MEI, MEII
A & P Mechanic
FAASTeam - Safer Skies Through Education
Professionalism in aviation is the pursuit of excellence through discipline, ethical behavior and continuous improvement. NBAA
Re: C172R & C172SP
A few things to keep in mind. Whether it's a 172R or S model, the props are still fixed pitch, and a compromise between climb and cruise. Diameter and pitch is set for maximum rated rpm while in cruise.
It takes a constant speed propellor, that can adjust pitch on the fly, to achieve full rpms on the takeoff roll. Full rpms mean more horsepower, and the available power will vary with density altitude. Higher the airport, and lower the power. Constant speeds are nice. But they're more expensive, and have a maintenance limitation, which costs even more money.
Note: there are also some props that adjust pitch, electrically. Cessna's, Pipers, and most other commercial produced airplanes with constant speed props, use a hydraulic/governor system.
Cessna 172N owners (as an example), might typically change props, for a preference of climb or cruise speeds.
It takes a constant speed propellor, that can adjust pitch on the fly, to achieve full rpms on the takeoff roll. Full rpms mean more horsepower, and the available power will vary with density altitude. Higher the airport, and lower the power. Constant speeds are nice. But they're more expensive, and have a maintenance limitation, which costs even more money.
Note: there are also some props that adjust pitch, electrically. Cessna's, Pipers, and most other commercial produced airplanes with constant speed props, use a hydraulic/governor system.
Cessna 172N owners (as an example), might typically change props, for a preference of climb or cruise speeds.
Re: C172R & C172SP
That's of course correct - bad wording from my, an example of me writing while looking stuff up from dusty manuals..Great Ozzie wrote:Well, there will have to be for the changes in Vso & Vs1.AKar wrote:I'm not sure if there are other differences in the indicator face.
Va is not on the ASI.
Good points too. Not talking about 172 per se, but often the owners who fly much glider towing, parachutists etc, wish to have the "climb prop" installed. The ones who generally fly longer trips don't really get much benefit from finer pitch props but instead wish to have "cruise propellers" in place for better cruise performance at reasonable rpm.L.A. wrote:A few things to keep in mind. Whether it's a 172R or S model, the props are still fixed pitch, and a compromise between climb and cruise. Diameter and pitch is set for maximum rated rpm while in cruise.
It takes a constant speed propellor, that can adjust pitch on the fly, to achieve full rpms on the takeoff roll. Full rpms mean more horsepower, and the available power will vary with density altitude. Higher the airport, and lower the power. Constant speeds are nice. But they're more expensive, and have a maintenance limitation, which costs even more money.
Note: there are also some props that adjust pitch, electrically. Cessna's, Pipers, and most other commercial produced airplanes with constant speed props, use a hydraulic/governor system.
Cessna 172N owners (as an example), might typically change props, for a preference of climb or cruise speeds.
As far as I understand the electrical pitch adjusting systems are mostly used in very light aircraft, motor gliders etc due to weight savings. The hydraulic system is easy to do mechanically with flyweight governors and piston, and is rather reliable and can also be made fail-safe in multi-engined configurations. In larger aircraft, it's a bit of combination as the actuating system is hydraulic, but the inputs to it come at least partially from FADEC/EEC.
-Esa
Re: C172R & C172SP
As far as I understand the electrical pitch adjusting systems are mostly used in very light aircraft, motor gliders etc due to weight savings. The hydraulic system is easy to do mechanically with flyweight governors and piston, and is rather reliable and can also be made fail-safe in multi-engined configurations. In larger aircraft, it's a bit of combination as the actuating system is hydraulic, but the inputs to it come at least partially from FADEC/EEC.
There are higher performance "experimentals", that use elec variable pitch props, because of auto engine conversions for aircraft. I admit, I don't like them, and prefer the flyweight, governor, and piston. Airplane engines setup for constant speed props, have a hollow crankshaft, for the oil travel to the prop piston. WWII, fighters, such as the P-40 also had electric props, while the P-51 is a hydraulic constant speed.
- Great Ozzie
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Re: C172R & C172SP
Oh no I appreciated it...AKar wrote: That's of course correct - bad wording
Gave me an opportunity to both be persnickety and give you a hard time.
Rob Osborne
Flight Instructor - CFI, CFII, MEI, MEII
A & P Mechanic
FAASTeam - Safer Skies Through Education
Professionalism in aviation is the pursuit of excellence through discipline, ethical behavior and continuous improvement. NBAA
Flight Instructor - CFI, CFII, MEI, MEII
A & P Mechanic
FAASTeam - Safer Skies Through Education
Professionalism in aviation is the pursuit of excellence through discipline, ethical behavior and continuous improvement. NBAA
Re: C172R & C172SP
That's perfect, Sir. As my since passed colleague once said, it's important to be corrected, otherwise we never know when we f**k up.Great Ozzie wrote: Oh no I appreciated it...
Gave me an opportunity to both be persnickety and give you a hard time.
Of course, the WWII planes used these also. They also had direct fuel injections, etc. 70 years ahead of their time?L.A. wrote:There are higher performance "experimentals", that use elec variable pitch props, because of auto engine conversions for aircraft. I admit, I don't like them, and prefer the flyweight, governor, and piston. Airplane engines setup for constant speed props, have a hollow crankshaft, for the oil travel to the prop piston. WWII, fighters, such as the P-40 also had electric props, while the P-51 is a hydraulic constant speed.
-Esa
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