---------------------------------------------------------- RV7-List Digest Archive --- Total Messages Posted Wed 07/07/04: 8 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 11:03 AM - Re: Aerobatics with FP prop (rv6capt@pacificcoast.net) 2. 02:39 PM - Re: Aerobatics with FP prop (Robert Lake) 3. 03:44 PM - SEC: UNCLASSIFIED Re: Aerobatics with FP prop (Francis, David CMDR) 4. 04:28 PM - Re: UNCLASSIFIED Re: Aerobatics with FP prop (sjevans) 5. 06:05 PM - Re: UNCLASSIFIED Re: Aerobatics with FP prop (cary rhodes) 6. 10:28 PM - SEC: UNCLASSIFIED Re: Aerobatics with FP prop (Francis, David CMDR) 7. 10:53 PM - Re: UNCLASSIFIED Re: Aerobatics with FP prop (Dan Checkoway) 8. 11:39 PM - SEC: UNCLASSIFIED Re: Aerobatics with FP prop (Francis, David CMDR) ________________________________ Message 1 _____________________________________ Time: 11:03:15 AM PST US From: rv6capt@pacificcoast.net Subject: Re: RV7-List: Aerobatics with FP prop --> RV7-List message posted by: rv6capt@pacificcoast.net I do all the aerobatics metioned in Vans construction manual with no problems with the fixed pitch prop, including 1 1/4 to 1 1/2 rotations in a vertical climb. Quoting Allen Fulmer : > --> RV7-List message posted by: "Allen Fulmer" > > I am trying to decide the Fixed Pitch/Constant Speed Prop question. Lots of > interesting opinions/experiences on the list lately. One thing I have not > seen mentioned is whether the mild, positive G aerobatics I want to be able > to do can be done as well with a FP prop as with a CS? > > Opinions/experience? > > Thanks, > > Allen Fulmer > RV7 Wings > N808AF reserved > > > > > > ________________________________ Message 2 _____________________________________ Time: 02:39:16 PM PST US From: Robert Lake Subject: Re: RV7-List: Aerobatics with FP prop --> RV7-List message posted by: Robert Lake Gentlemen: I am in the middle of a RV-7 and have decided on a fixed pitch prop. It's a cost factor. I've got an IO-360 A1A. A C/S prop is $5,000....and the governor cost....and the costs every year for the additional inspections during the annual........ Anyway, Van's told me that the cruise speed will be just about the same with a fixed pitch and I will only give up about 200 feet with the take-off roll. Bob Lake Austin, Tx ----- Original Message ----- From: "Allen Fulmer" Subject: RV7-List: Aerobatics with FP prop > --> RV7-List message posted by: "Allen Fulmer" > > I am trying to decide the Fixed Pitch/Constant Speed Prop question. Lots of > interesting opinions/experiences on the list lately. One thing I have not > seen mentioned is whether the mild, positive G aerobatics I want to be able > to do can be done as well with a FP prop as with a CS? > > Opinions/experience? > > Thanks, > > Allen Fulmer > RV7 Wings > N808AF reserved > > ________________________________ Message 3 _____________________________________ Time: 03:44:34 PM PST US From: "Francis, David CMDR" Subject: SEC: UNCLASSIFIED RE: RV7-List: Aerobatics with FP prop --> RV7-List message posted by: "Francis, David CMDR" Allen, Aeros with a fixed pitch prop can be done. The main impact of a CS prop is lower workload for the pilot and kinder treatment to the engine. The governor ensures that the engine is neither oversped nor overtorqued during aeros. With FP the pilot becomes the governor. Personnally I would not pay the huge price premium just to get lower workload aerobatics. The large price premium for a CS prop buys versatility. The compromise involved with a FP prop is removed at a price and weight premium. What you get is shorter takeoff, better climb, and same cruise speed (compared to a cruise FP prop). Additionally, if you also have fuel injection and an engine analyser a CS prop means you can more accurately optimise the MAP/rpm? mixture to run lean of peak and get very good miles per gallon in the cruise. Generally (with many exceptions) engine cofigurations fall into two opposite camps: a. low cost high fuel consumption - carburettor, magnetos, fixed pitch, simple instruments, or b. high cost, low fuel consumption - injected, electronic ignition, constant speed, engine analyzer. Combinations in between tend to be inefficient comromises. Regards, David Francis, Canberra Australia, RV7, airframe complete, ordering the engine. Subject: Re: RV7-List: Aerobatics with FP prop --> RV7-List message posted by: rv6capt@pacificcoast.net I do all the aerobatics metioned in Vans construction manual with no problems with the fixed pitch prop, including 1 1/4 to 1 1/2 rotations in a vertical climb. Quoting Allen Fulmer : > --> RV7-List message posted by: "Allen Fulmer" > > I am trying to decide the Fixed Pitch/Constant Speed Prop question. Lots of > interesting opinions/experiences on the list lately. One thing I have not > seen mentioned is whether the mild, positive G aerobatics I want to be able > to do can be done as well with a FP prop as with a CS? > > Opinions/experience? > > Thanks, > > Allen Fulmer > RV7 Wings > N808AF reserved > > > > > > ________________________________ Message 4 _____________________________________ Time: 04:28:47 PM PST US From: "sjevans" Subject: RE: UNCLASSIFIED RE: RV7-List: Aerobatics with FP prop --> RV7-List message posted by: "sjevans" David, My plan at this time is a 360 engine with a FP prop. I am planning to use electronic ignition on one side to help smooth-out the engine & improve performance. Are you saying this combination is an "inefficient compromise"? I'm sort of new at this, so if there is something I'm missing, please let me know. I sure don't want to spend extra bucks if I'm not going to realize any benefit. Thanks, Sam Evans Working on wings N350SE, reserved -----Original Message----- From: owner-rv7-list-server@matronics.com [mailto:owner-rv7-list-server@matronics.com] On Behalf Of Francis, David CMDR Subject: SEC: UNCLASSIFIED RE: RV7-List: Aerobatics with FP prop --> RV7-List message posted by: "Francis, David CMDR" Allen, Aeros with a fixed pitch prop can be done. The main impact of a CS prop is lower workload for the pilot and kinder treatment to the engine. The governor ensures that the engine is neither oversped nor overtorqued during aeros. With FP the pilot becomes the governor. Personnally I would not pay the huge price premium just to get lower workload aerobatics. The large price premium for a CS prop buys versatility. The compromise involved with a FP prop is removed at a price and weight premium. What you get is shorter takeoff, better climb, and same cruise speed (compared to a cruise FP prop). Additionally, if you also have fuel injection and an engine analyser a CS prop means you can more accurately optimise the MAP/rpm? mixture to run lean of peak and get very good miles per gallon in the cruise. Generally (with many exceptions) engine cofigurations fall into two opposite camps: a. low cost high fuel consumption - carburettor, magnetos, fixed pitch, simple instruments, or b. high cost, low fuel consumption - injected, electronic ignition, constant speed, engine analyzer. Combinations in between tend to be inefficient comromises. Regards, David Francis, Canberra Australia, RV7, airframe complete, ordering the engine. Subject: Re: RV7-List: Aerobatics with FP prop --> RV7-List message posted by: rv6capt@pacificcoast.net I do all the aerobatics metioned in Vans construction manual with no problems with the fixed pitch prop, including 1 1/4 to 1 1/2 rotations in a vertical climb. Quoting Allen Fulmer : > --> RV7-List message posted by: "Allen Fulmer" > > I am trying to decide the Fixed Pitch/Constant Speed Prop question. Lots of > interesting opinions/experiences on the list lately. One thing I have not > seen mentioned is whether the mild, positive G aerobatics I want to be able > to do can be done as well with a FP prop as with a CS? > > Opinions/experience? > > Thanks, > > Allen Fulmer > RV7 Wings > N808AF reserved > > > > > > == == == == ________________________________ Message 5 _____________________________________ Time: 06:05:45 PM PST US From: cary rhodes Subject: RE: UNCLASSIFIED RE: RV7-List: Aerobatics with FP prop --> RV7-List message posted by: cary rhodes sam don't back off on the electronic ign. You will be sorry if u stick with the dual mags. just my 2 cents cary --- sjevans wrote: > --> RV7-List message posted by: "sjevans" > > > David, > My plan at this time is a 360 engine with a FP > prop. I am planning to > use electronic ignition on one side to help > smooth-out the engine & > improve performance. Are you saying this > combination is an "inefficient > compromise"? > I'm sort of new at this, so if there is something > I'm missing, please > let me know. I sure don't want to spend extra bucks > if I'm not going to > realize any benefit. > Thanks, > Sam Evans > Working on wings > N350SE, reserved > > -----Original Message----- > From: owner-rv7-list-server@matronics.com > [mailto:owner-rv7-list-server@matronics.com] On > Behalf Of Francis, David > CMDR > To: 'rv7-list@matronics.com' > Subject: SEC: UNCLASSIFIED RE: RV7-List: Aerobatics > with FP prop > > --> RV7-List message posted by: "Francis, David > CMDR" > > > > Allen, > Aeros with a fixed pitch prop can be done. The main > impact of a CS prop > is > lower workload for the pilot and kinder treatment to > the engine. The > governor ensures that the engine is neither oversped > nor overtorqued > during > aeros. With FP the pilot becomes the governor. > > Personnally I would not pay the huge price premium > just to get lower > workload aerobatics. The large price premium for a > CS prop buys > versatility. > The compromise involved with a FP prop is removed at > a price and weight > premium. What you get is shorter takeoff, better > climb, and same cruise > speed (compared to a cruise FP prop). Additionally, > if you also have > fuel > injection and an engine analyser a CS prop means you > can more accurately > optimise the MAP/rpm? mixture to run lean of peak > and get very good > miles > per gallon in the cruise. > > Generally (with many exceptions) engine > cofigurations fall into two > opposite > camps: > a. low cost high fuel consumption - carburettor, > magnetos, fixed pitch, > simple instruments, or > b. high cost, low fuel consumption - injected, > electronic ignition, > constant > speed, engine analyzer. > > Combinations in between tend to be inefficient > comromises. > > Regards, > David Francis, Canberra Australia, RV7, airframe > complete, ordering the > engine. > > > Subject: Re: RV7-List: Aerobatics with FP prop > > > --> RV7-List message posted by: > rv6capt@pacificcoast.net > > I do all the aerobatics metioned in Vans > construction manual with no > problems > with the fixed pitch prop, including 1 1/4 to 1 1/2 > rotations in a > vertical > climb. > > Quoting Allen Fulmer : > > > --> RV7-List message posted by: "Allen Fulmer" > > > > > I am trying to decide the Fixed Pitch/Constant > Speed Prop question. > Lots > of > > interesting opinions/experiences on the list > lately. One thing I have > not > > seen mentioned is whether the mild, positive G > aerobatics I want to be > able > > to do can be done as well with a FP prop as with a > CS? > > > > Opinions/experience? > > > > Thanks, > > > > Allen Fulmer > > RV7 Wings > > N808AF reserved > > > > > > > > > > > > > > > == > == > == > == > > > > Contributions > any other > Forums. > > http://www.matronics.com/chat > > http://www.matronics.com/subscription > http://www.matronics.com/FAQ/RV7-List.htm > http://www.matronics.com/archives > http://www.matronics.com/photoshare > http://www.matronics.com/emaillists > > > > > > __________________________________ http://promotions.yahoo.com/new_mail ________________________________ Message 6 _____________________________________ Time: 10:28:02 PM PST US From: "Francis, David CMDR" Subject: SEC: UNCLASSIFIED RE: RV7-List: Aerobatics with FP prop --> RV7-List message posted by: "Francis, David CMDR" Sam, The answer depends on your choice of fuel delivery system. I shall explain. Starting point - a carburetted engine must cruise rich of peak, where fuel is used to cool the interior of the cylinder. Fuel injection has better fuel delivery to cylinders, and it is therefore possible to cruise lean of peak where air is used to cool the inside of a cylinder. Major fuel savings in the cruise are possible. A magneto delivers spark at fixed timing of 25 degrees BTDC. The engineers chose 25BTDC because it provides adequate performance at full power, and is optimum for rich of peak cruise at around 2400rpm. These are conditions typical for a carburetted engine. Now electronic ignition provides three benefits - variable timing, a hotter spark, and a longer duration spark. Electronic ignition on a carburetted engine will self-select 15BTDC in the cruise - because it is the optimum. So apart from easier starting and a slight advantage from a hotter & longer spark, its performing the same as a much cheaper magneto. Not a good choice. Now if you have electronic ignition on a fuel injected engine, and you choose to cruise lean of peak, then the flame front slows down. The ignition will compensate and optimise timing by advancing it to maybe 40BTDC. This generates major improvements in miles per gallon. You will fly a little slower, with a big improvement in mpg. Electronic ignition plus fuel injection should definitely pay for themselves in fuel savings, and more. Improvements in fuel efficiency compared to rich of peak in the range of 15%-25% are possible. A CS prop can add a little more to fuel efficiency by allowing wide open throttle and oversquare operations and also operations above 10,000 ft as follows. The optimum cruise altitude for a normally aspirated plane is in the region 8000-9500 depending on seasonal temperature. The peak torque in an 0360 from Aerosport occurs at 2300rpm. So the optimum cruise is 8000 or so ft, wide open throttle, 2300 rpm, lean of peak. With FP prop hitting this combination is a hit or miss affair, but not with a CS prop. Also to go above 10,000 to take advantage of drag reduction/improved TAS you need to restore lost engine power by selecting a higher rpm - 2450 for instance, which is unavailable in a FP installation. That is how Jon Johanson gets extraordinarily good fuel efficiency on his long range flights. Need oxy of course. To confirm this short story read: for running lean of peak, the Pelicans Perch articles by John Deakin on Avweb, and also see the GAMI site. for electronic ignition the research papers on the CAFE site. for a good knowledge of your 0360 the Skyranch Engineering Manual. Have fun, David Francis, Canberra, Australia. --> RV7-List message posted by: "sjevans" David, My plan at this time is a 360 engine with a FP prop. I am planning to use electronic ignition on one side to help smooth-out the engine & improve performance. Are you saying this combination is an "inefficient compromise"? I'm sort of new at this, so if there is something I'm missing, please let me know. I sure don't want to spend extra bucks if I'm not going to realize any benefit. Thanks, Sam Evans Working on wings N350SE, reserved ________________________________ Message 7 _____________________________________ Time: 10:53:23 PM PST US From: "Dan Checkoway" Subject: Re: UNCLASSIFIED RE: RV7-List: Aerobatics with FP prop --> RV7-List message posted by: "Dan Checkoway" > Starting point - a carburetted engine must cruise rich of peak, where fuel > is used to cool the interior of the cylinder. Fuel injection has better fuel > delivery to cylinders, and it is therefore possible to cruise lean of peak > where air is used to cool the inside of a cylinder. Major fuel savings in > the cruise are possible. Possible...only if you have the appropriate equipment. Specifically, balanced injectors. LOP operation isn't something that any old fuel injected engine should be subjected to. Probably what you meant, but I wanted to clarify for the record. 8-) )_( Dan RV-7 N714D http://www.rvproject.com ________________________________ Message 8 _____________________________________ Time: 11:39:38 PM PST US From: "Francis, David CMDR" Subject: SEC: UNCLASSIFIED RE: RV7-List: Aerobatics with FP prop --> RV7-List message posted by: "Francis, David CMDR" Dan, You are correct, the injectors need to be balanced. Additionally, in the interest of keeping a long story short, I did not mention the need for good instrumentation to support LOP - as a minimum you need EGT and EGT for all cylinders, and an accurate fuel flow meter is highly recommended too. Regards, David Francis, Canberra, Australia, in the middle of a dry, cold windy winter. --> RV7-List message posted by: "Dan Checkoway" > Starting point - a carburetted engine must cruise rich of peak, where fuel > is used to cool the interior of the cylinder. Fuel injection has better fuel > delivery to cylinders, and it is therefore possible to cruise lean of peak > where air is used to cool the inside of a cylinder. Major fuel savings in > the cruise are possible. Possible...only if you have the appropriate equipment. Specifically, balanced injectors. LOP operation isn't something that any old fuel injected engine should be subjected to. Probably what you meant, but I wanted to clarify for the record. 8-) )_( Dan RV-7 N714D http://www.rvproject.com _-