Jamie

Jamie

Well Known Member
I am based at a towered airport (LZU) with a 6000ft runway. Yesterday evening I went out for some "therapy" as I like to call it. In spite of a light breeze across the ground and some serious winds at altitude, the air was smooth as silk. Heading back to home base I was northeast of the field and I was told to make a left downwind to runway 7. I was the only one around. When I was abeam the departure end on downwind I was doing 185kts TAS, 195kts groundspeed. Abeam the approach end I was doing 80kts TAS.

That, ladies and gentleman, is why you get a C/S prop. It's also why I sort of chuckle when people talk about putting speed brakes on these airplanes.

BTW: Before someone scolds me about this...I don't make a habit of this. I know it's not 'good' for the engine. Believe it or not, I did pull the power off slowly. Also, I would never do this at a non-towered airport.
 
I agree with the nice braking effects of C/S and I'm not scolding but ... Why would you not conform to FAR 91 limitations of 156 knots in the pattern for piston aircraft? And why would you not fly similarly at a non-towered airport?
 
Well OK, but ...

I have the Hartzell B/A C/S 72" prop on my RV-6A and previously I had a non-blended airfoil prop with F7666 blades. I'm sure there is some drag effect but I don't notice it - yes really. When I come in from a speed run and throttle back and the MAP bleeds off I go to fine pitch max RPM prop setting and I still have to pull back on the stick and trim the nose up to slow the plane to flap speed and it doesn't happen fast even then. I then slip the plane for a short approach and landing. I don't think there should be a lusting for this prop with the thought that it is going to react like a reversible prop to slow the plane down. If I were to do it over I would get a custom fixed pitch prop for maximum speed at sea level or maybe 1,000 ft, and for landing operations, pull the nose up for deceleration to flap speed and slip for the altitude and speed control on landing. I have enough excess power to make a normal takeoff with my stock O-360-A1A from most airports. What the C/S prop gives me I think is assurance that it will perform well under all circumstances.

Bob Axsom
 
Isn't it actually...

tdhanson said:
I agree with the nice braking effects of C/S and I'm not scolding but ... Why would you not conform to FAR 91 limitations of 156 knots in the pattern for piston aircraft? And why would you not fly similarly at a non-towered airport?
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...200 kts? And it's IAS in the FARs not TAS....:)

Sec. 91.117 ? Aircraft speed.
(a) Unless otherwise authorized by the Administrator, no person may operate an aircraft below 10,000 feet MSL at an indicated airspeed of more than 250 knots (288 m.p.h.).

(b) Unless otherwise authorized or required by ATC, no person may operate an aircraft at or below 2,500 feet above the surface within 4 nautical miles of the primary airport of a Class C or Class D airspace area at an indicated airspeed of more than 200 knots (230 mph.). This paragraph (b) does not apply to any operations within a Class B airspace area. Such operations shall comply with paragraph (a) of this section.
 
It's not uncommon for me to enter the pattern at 180 IAS and be at 100 IAS while turning base with my fixed pitch prop. These airplanes slow down just fine if you fly them instead of just sitting there waiting for them to slow down.

I do think CS helps with the short field landings where you get a quick burst of forward speed do to reduced drag in ground effect. Maybe 30 feet or so?
 
tdhanson said:
I agree with the nice braking effects of C/S and I'm not scolding but ... Why would you not conform to FAR 91 limitations of 156 knots in the pattern for piston aircraft? And why would you not fly similarly at a non-towered airport?
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Where is that at? I just searched my FAR/AIM and couldn't find it. I found a reference on some websites to FAR 91.70B but that doesn't appear to exist in my copy. :)
 
Jamie said:
......It's also why I sort of chuckle when people talk about putting speed brakes on these airplanes......
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To achieve maximum performance, a constant speed prop is nice, no question about it ....but when it comes to slowing down.....is not all that superior to an efficient fixed pitch prop. Certainly, some RV's do sport fixed pitch props less efficient than others. With various passenger/witnesses onboard my Sensenich equipped -6A, I have often demonstrated just how easy it is to slow down in the pattern.

Here is a (RV-8 builder) first hand eyewitness account as he observed it. See post #112:
http://www.vansairforce.com/communi...hlight=constant+speed+pattern+altitude&page=6


Typically indicating 185-200 MPH, I can easily cross over the field at pattern altitude, fly a tight pattern and without excessively chopping the power can and do slow to Vfe somewhere in the circled area of downwind and base leg.

24qvdx4.jpg


If a given fixed pitch RV cannot fly a profile as outlined above, I submit their fixed pitch prop is not nearly as efficient as my faster than a constant speed and nearly bulletproof Sensenich. :)

15y98jq.jpg
 
hevansrv7a said:
Do I misremember or is Bob Axom's top speed about 182?
Tell us how you made your airplane that fast, please :).
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No doubt Bob can beat me at straight and level flight. At WOT at 8000FT I do 178kts when light. I was descending to the airport and was doing about 190 TAS before leveling out so I had momentum on my side and my speed was already bleeding off.
 
You're right. Doesn't appear in my 2007 FAR/AIM hardcopy either. I used a handout my CFI gave me. I did find it mentioned in two web references. I guess it's a caviat to treat web info with some scepticism. Is this old info?

http://books.google.com/books?id=bE...0CAYQ6AEwAA#v=onepage&q=far 91.70 156&f=false

http://avstop.com/ac/flighttrainghandbook/airporttrafficpatterns.html


I found it: Seems to be based on OLD 1985 regs:
http://rgl.faa.gov/Regulatory_and_G...52567a8005f57c2!OpenDocument&ExpandSection=-4
 
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If I remember correctly it was raised to 200 kts sometime in the early 90's. Maybe the change had something to do with converting to ICAO airspace classifications..?
 
If a given fixed pitch RV cannot fly a profile as outlined above, I submit their fixed pitch prop is not nearly as efficient as my faster than a constant speed and nearly bulletproof Sensenich.
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I wonder how much longer it took your "faster" fp prop to climb to 8000', and also how much faster the Hartzell would be if you wound it up to 2730 RPM? BTW, I though the Sensenich was limited to 2600 RPM?
 
Overhead approach

At a towered airport, just ask for an overhead approach. You can come in at cruise speed and be at flap speed by the time you roll out on downwind. Works with either prop :)
 
FP/CS

One more good reason for a CS prop.
This observation is based on actual experience selling my FP Sensenich Prop RV-8
When its time to sell, everybody wants a CS Prop.
 
JBW said:
I wonder how much longer it took your "faster" fp prop to climb to 8000', and also how much faster the Hartzell would be if you wound it up to 2730 RPM? BTW, I though the Sensenich was limited to 2600 RPM?
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I cannot answer for others but I can for my airplane. With my IO-340 with 3 blade fixed pitch Catto prop from a field elevation of 1300' it takes me 2 minutes to 4500', 4 minutes to 6500', 6 minutes to 8500'.
 
Jamie said:
I am based at a towered airport (LZU) with a 6000ft runway. Yesterday evening I went out for some "therapy" as I like to call it. In spite of a light breeze across the ground and some serious winds at altitude, the air was smooth as silk. Heading back to home base I was northeast of the field and I was told to make a left downwind to runway 7. I was the only one around. When I was abeam the departure end on downwind I was doing 185kts TAS, 195kts groundspeed. Abeam the approach end I was doing 80kts TAS.

That, ladies and gentleman, is why you get a C/S prop. It's also why I sort of chuckle when people talk about putting speed brakes on these airplanes.

BTW: Before someone scolds me about this...I don't make a habit of this. I know it's not 'good' for the engine. Believe it or not, I did pull the power off slowly. Also, I would never do this at a non-towered airport.
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Cool maneuver, but I remain unconvinced.

When compared with no other factors maybe CS is the way to go. But factor in weight (plus 50#) and cost (plus $7000) and complexity (moving parts that can fail) boat anchor performance (with an engine failure), forget it.

These airplanes do just fine with simple FP, 10,000' in a little over 8 minutes. :)
 
So when I hoof it downwind in an A320 -1500'agl at 340kts IAS, am I breaking a rule somewhere.......:D

It slows down really well, by base turn you are at 210, flap 1, half way round base, 185, flap 2 then gear down, turn final at 800', 170, flap 3, then flap full, stable at 500', checks complete.

:rolleyes:
 
David-aviator said:
boat anchor performance (with an engine failure)
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I find that to be an exaggerated, unfounded claim as well. I have intentionally dead sticked my airplane a number of times. It glides perfectly fine with the red knob all the way back.
 
You are right of course.....

Kevin Horton said:
Not quite true. There have been many amendments that added even numbered FARs, such as 91.126, 91.130, 91.138, 23.2, 23.302, 23.1322, etc.
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That's why the even numbers were left out in the first place.
 
Up here in the higher elevations of the mountain west............C/S props are just favored. No if or buts about it. Faster takeoff, better climb, and braking ability. We can get our planes down quickly if needed. It just won't happen with a fixed pitch prop that's compromised somewhere between climb and cruise. I hear that the difference between C/S and F/P isn't as vast at lower altitudes............but then I wouldn't know. I've never took off from less than 2000' msl. And yes, I'll often enter the pattern rather quickly too. Just depends on traffic.

L.Adamson ---- RV6A , Hartzell CS
 
RVbySDI said:
I cannot answer for others but I can for my airplane. With my IO-340 with 3 blade fixed pitch Catto prop from a field elevation of 1300' it takes me 2 minutes to 4500', 4 minutes to 6500', 6 minutes to 8500'.
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So your average ROC from 1300' to 8500' is 1200 fpm:rolleyes:I suspect that with a CS prop you could probably cut that 6 minutes nearly in half AND not give away any cruise speed once you got there.
 
Rick6a said:
To achieve maximum performance, a constant speed prop is nice, no question about it ....but when it comes to slowing down.....is not all that superior to an efficient fixed pitch prop. Certainly, some RV's do sport fixed pitch props less efficient than others. With various passenger/witnesses onboard my Sensenich equipped -6A, I have often demonstrated just how easy it is to slow down in the pattern.
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At my airport altitudes in the Rocky's...........I've been around too many Senenich metal props, that don't stand a chance in slowing down nearly as fast, as we can with the C/S. However, it has been mentioned that the differences are less......at lower altitudes. Perhaps it's true. BTW.... my pattern would normally be a lot less from the base turn to runway, than in the diagram. And at higher altitudes, my ground speed will be higher also.

L.Adamson ---- RV6A
 
The counter argument is that my little 'ol RV-6 with its lightweight wooden prop has more enjoyable flying characteristics than the airplanes with 50+ pounds of prop and governor on the nose.

It's the Porsche vs Corvette argument. That big V-8 sure launches the 'Vette, but the Porsche is a better driving experience.

Just sayin...
 
Kyle Boatright said:
The counter argument is that my little 'ol RV-6 with its lightweight wooden prop has more enjoyable flying characteristics than the airplanes with 50+ pounds of prop and governor on the nose.

It's the Porsche vs Corvette argument. That big V-8 sure launches the 'Vette, but the Porsche is a better driving experience.

Just sayin...
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Being a 2010 Shelby GT500 owner, I have to say that nothing, and I mean nothing compares to that V8 power and sound.....meaning I'll take the 50lbs penalty to reap the CS rewards.....to each their own I suppose
 
Do we have to keep arguing over the same issues???

Guys, there are just way too many factors in each builder's profile, and threads like this do nothing but drift to Porsche's vs. Corvette's or whatever.

Get what you want/need/can afford, and be done with it.

I mean no offense to you Jamie...cool performance, but the thread is going in the direction they all go...:rolleyes:

:cool:
 
Well said...

cjensen said:
Do we have to keep arguing over the same issues???

Guys, there are just way too many factors in each builder's profile, and threads like this do nothing but drift to Porsche's vs. Corvette's or whatever.

Get what you want/need/can afford, and be done with it.

I mean no offense to you Jamie...cool performance, but the thread is going in the direction they all go...:rolleyes:

:cool:
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I have flown both and they really can not be compared. They each have their own pluses and minuses. Any RV with an appropriate prop is a good airplane.
 
Jamie said:
...I have intentionally dead sticked my airplane a number of times. It glides perfectly fine with the red knob all the way back.
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Jamie, did you find the pitch control worked with the dead engine? I have tested at idle and a course pitch improves the glide ratio, but wondered if it would work with a windmilling prop?
BTW, I have had sensenich 85 and 87 inch and Hatzel BA (now) on my RV7. I think the Sensenichs were faster but will keep the CS. I like the way I can control speed while landing and the effect it has on weight and bal on the RV7. I liked them both however but for different reasons. Both are accepatble choices to me.
 
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Kyle Boatright said:
The counter argument is that my little 'ol RV-6 with its lightweight wooden prop has more enjoyable flying characteristics than the airplanes with 50+ pounds of prop and governor on the nose.

It's the Porsche vs Corvette argument. That big V-8 sure launches the 'Vette, but the Porsche is a better driving experience.

Just sayin...
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That's a matter of opinion. I'd take a ZO6 over a Carerra anyday! :D
 
Annomoly

I must be an odd ball. I'd take a Porsche over a 'vette. I'd take a c/s prop over a fp.;)
I will be going with a c/s because most of my time is in airplanes with c/s props, and I really like the ability to maintain a constant RPM regardless of throttle/airspeed combinations.
 
JBW said:
So your average ROC from 1300' to 8500' is 1200 fpm:rolleyes:I suspect that with a CS prop you could probably cut that 6 minutes nearly in half AND not give away any cruise speed once you got there.
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I agree that would be a kick but I still can't complain about 1200 fpm. I guess I haven't been spoiled yet. :D
 
FP vs CS

Remember Chas Lindberg's work on US fighters in the Pacific? He extended their range significantly by running oversquare (minimizing internal friction IIRC) and leaning aggressively. This plus smoothness and quietness might be argument for the CS. Lycoming allows oversquare ops on the IO-360's and 540's. I often run 2200/24 inches or 21/2300 on the Lance for those reasons. Has anybody documented fuel svgs at constant power with this technique? If the -8 ever flies I'll try to with data from the AFS and Dynon.
 
mike newall said:
So when I hoof it downwind in an A320 -1500'agl at 340kts IAS, am I breaking a rule somewhere.......:D
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If you do this in U.S. airspace you are definitely in violation of the FAR's.

Within Class D airspace (or within the area of Class C airspace corresponding to Class D airspace) the speed limit is 200 kts indicated. Within Class B airspace the speed limit is 250 kts indicated.

In your own country's airspace, the rules may be different.

Pat
 
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