Golden State Ercoupe Owners Club, Region 7

Ercoupe Performance

>http://www.navmonster.com/

Also, Google earth will let you define a path and "fly", seeing the highways, mountains, etc. 

Ben Hampton from the tech list adds this; The very best flight planning for the money is using your EAA membership to get the DUATS Golden Eagle program.  It is the very best 'free'  flight planning package available.  It is exceptional software with to many features to list.  Rubber banding, down loadable to your GPS, muti-chart options, and strip maps just to name a very few.  Even if you do not belong to EAA, you can down load and use the system for $49 a year, as I recall.  There are more expensive super advanced versions for commercial pilots flying mostly IFR.  But the advanced systems are really not worth all that much for casual and VFR operation. 

>From AOPA;
A fuel-saving announcement from your ASI                 By Dave Hirschman

The airspeed indicator (ASI) can tell you a great deal about how to fly more efficiently, but few pilots know how to decode its drag-reducing, fuel-saving, and range-extending message.

According to Jack Norris, an aerospace engineer and technical director for the 1986 Voyager around-the-world flight, a simple, mechanical ASI (and an understanding of the aerodynamic drag chart and an airplane’s best rate of climb speed) is all we need to maximize speed vs. drag. Minimizing drag is the key to reducing fuel burn and extending range.

“The airspeed indicator tells us a lot more than just ram air pressure,” said Norris, author of The Logic of Flight, a self-published book on aircraft efficiency and propeller design. “Your ASI can also tell you the most logical and efficient way to fly without being wasteful of fuel or time.”

All pilots learn in ground school that any airplane’s best rate of climb and longest range is found at L/D max, that point on the drag chart where the induced and parasitic drag curves meet, and total drag is lowest. Pilots seeking peak efficiency can climb as high as possible and fly at L/D max for the absolute minimum fuel burn over the greatest distance.

But here in the real world, few of us would ever choose to fly so slowly.

“No one wants to plod along at some low speed with mushy controls,” said Norris, a private pilot for 60 years. “You do that if you’re flying the Voyager around the world. But even then, it took nine days, three minutes and 44 seconds. What we’re really looking for is flying as fast as possible with as little drag as possible.”

Norris points to what he calls the “Max Speed vs. Drag” point on the chart. There, pilots can gain 31 percent more speed while paying a paltry 15 percent drag penalty. Since true airspeed (TAS) increases with altitude, at 12,500 feet, for example, pilots can obtain an additional 21 percent payoff for a total 59 percent speed gain over L/D max.

“Who wouldn’t want to go 59 percent faster for 15 percent more drag?” Norris says. “Aerodynamics is full of tradeoffs—but this one’s a bargain.”

The best speed vs. drag point is always 1.31 times L/D max (or V_Y, the best-rate-of-climb speed), Norris says. Higher speeds are possible at lower altitudes and higher power settings. But since parasitic drag increases at the square of indicated airspeed, the additional speed carries a high price in dramatically higher fuel consumption and reduced range.

“Very few pilots really understand that the shape of the total drag curve is really a leaning, lazy J,” Norris says. “There’s a place where the curve flattens out and you can fly much faster for a very small increase in drag. You don’t need any special equipment or fancy math to figure it out. All you need to know is your aircraft’s V_Y and add 31 percent.”

Max efficiency profile
Norris recommends the following profile for virtually all piston-engine, general aviation aircraft: After takeoff, simply cruise climb at (1.31 times V_Y) as high as possible with the throttle wide open. When you’ve reached the maximum altitude at which you can maintain your target IAS with the mixture properly leaned, you’re done.

The pilot’s operating handbook for the AOPA’s IO-550-powered Beechcraft Bonanza BE36 seems to bear out Norris’ IAS-based strategy.

At a total weight of 3,400 pounds, V_Y is 96 knots, making the ideal target IAS 126 knots. On a standard day, with the throttle wide open and 2,500 rpm, mixture set 20 degrees lean of peak, the Bonanza shows 129 KIAS at 14,000 feet, 157 KTAS, and a fuel burn of 10.6 gph.

That’s about 14 KTAS less than the Bonanza’s best-power setting at 6,000 feet where the airplane travels 171 KTAS at 14.4 gph. So, on a 500-mile trip, flying at high altitude and optimal IAS adds less than 15 minutes flying time and saves 8.7 gallons of avgas (or more than $52 at current prices). Put another way, optimal IAS at altitude reduces speed 8.2 percent while slashing fuel consumption 20 percent.

Norris says his IAS-based approach works equally well for planes with fixed-pitch and constant-speed propellers and all engine sizes.

“Flying is subject to the same physical laws, and the drag curves apply to all aircraft,” he said. “Airplanes only know indicated airspeed. A wing doesn’t know how fast it’s moving over the ground, and it doesn’t care. Understanding IAS allows pilots to minimize drag, fly more intelligently, and get the most efficiency and utility out of their aircraft.”

Give it a try.       Try Norris’ IAS method and let us know how it works for you.

Environmental factors such as winds aloft and icing levels are sure to influence your aeronautical decisions. One rule of thumb is to climb as quickly as possible when tailwinds are present to maximize the time such favorable conditions can act upon your aircraft. In strong headwinds, lower groundspeeds at altitude can negate any gains in TAS or reductions in hourly fuel burn.

Also, physiological factors and the availability of supplemental oxygen can come into play at the higher altitudes Norris’ IAS-based strategy suggests. Federal aviation regulations mandate that pilots use of supplemental oxygen whenever they’re above 12,500 feet cabin pressure altitude more than 30 minutes, and at all times above 14,000 feet. (But studies show hypoxia can begin at significantly lower altitudes for many people, and headaches, dehydration, and fatigue are common after prolonged periods at 8,000 or 10,000 feet without supplemental oxygen.)

Are you willing to fly higher and give up some speed for better fuel efficiency? Have fuel price increases changed the way to operate your aircraft? Share your thoughts and efficiency strategies on Hirschman’s blog.

Courtesy of Percy Wood in AZ;

>Dave Hirschman wrote:
"According to Jack Norris, an aerospace engineer and technical director for the 1986 Voyager around-the-world flight, a simple, mechanical ASI (and an understanding of the aerodynamic drag chart and an airplanes best rate of climb speed) is all we need to maximize speed vs. drag. Minimizing drag is the key to reducing fuel burn and extending range."

I purchased the book.  The proposition is quite simple; Total Drag = Parasite Drag + Induced Drag. 

Total Drag is what you pay for.  Parasite Drag comes from pushing the plane through the air AND GOES UP WITH THE SQUARE OF THE AIRSPEED.  Induced Drag comes from lifting the weight of plane, pilot(s), et al, up into the air AND GOES DOWN WITH THE SPEED.

By plotting airspeed vs. the two drags, one sees that they cross at some point (PD = ID).  This point is the "bottom of the Drag Bucket;" a low area where drag is almost constant over a range of airspeeds.   At the upper end is where you run; a little more drag for the best speed.

And this is only the first trick.  The rest of the story involves flying at the highest usable altitude (10,000 ft MSL for Sport Pilots) with the openest throttle and leaned the best.  So flying slower saves
money!

The final trick uses the first two to avoid fuel stops.  Not only do you "keep on truckin'" while the fasties are on the ground, but you are spared the descent/climb cycle.  You get to the "hundred-dollar
hamburger" before they do! 

As a final note.  All this wisdom is only directly available with an accurate airspeed indicator.  Many `coupes don't have that.
So read that piece when Ed gets it transferred from "fly-in." Percy in NM, USA  

>Ed Burkhead shares this propeller & cruise speed info;

My observation on cruise speed and pitch with the C-85:

All observations at 2400 rpm
7146   100 mph       climb prop
7148   104 mph       normal prop (per Ed and John)
7150   108 mph       cruise prop (per Ed and John)
7150   112 mph       theoretical – several heavy or draggy Coupes have shown they can only make it to 90 mph with miserable climb using this pitch.

These correspond pretty well between my observations/measurements and Paul Prentice’s information duplicated below.

Propeller - perfomance & efficiency;

From the Ercoupe Tech list (courtesy of Ed Burkhead);

Paul Prentice published tables in his 1991 book "Fly About Adventures and the Ercoupe." His tables have checked out pretty well, from my experience with measured speeds during in-flight observations. Ed Burkhead

The following material is used by permission of the author and copyright holder, Paul Prentice.  Paul may be contacted at Flyabout1@cs.com to request permission for any other use. All rights reserved.  For each engine, these are at the "recommended cruising RPM according to the "Operators Manual" by Teledyne Continental Motors Form X30012 FAA approved Dec. 1980.
 
All numbers @ 5.1 degrees Celsius @ 5,000 feet.
C-75 @ RPM=2275    prop=CL7349    IAS=102    TAS=110
                   prop=ST7351    IAS=106    TAS=114
                   prop=CR7353    IAS=111    TAS=119
 
C-90 @ RPM=2350    prop=CL7150    IAS=106    TAS=114
                   prop=ST7152    IAS=110    TAS=118
                   prop=CR7153    IAS=114    TAS=123

C-85 @ RPM=2400    prop=CL7148    IAS=104    TAS=112
                   prop=ST7150    IAS=108    TAS=116
                   prop=CR7152    IAS=112    TAS=121

O-200 @ RPM=2500   prop=CL6948    IAS=103    TAS=111
                   prop=ST6950    IAS=108    TAS=116
                   prop=CR6952    IAS=112    TAS=121
 
For comparison:  The C-85 with a 50 inch pitch prop.  The 50 inch pitch means it would theoretically travel 50 inches forward during one turn.
 
113.6 miles/hour = (50 inches * 2400 rev/min * 60 min/hour ) / (12 inches/foot) / (5280 feet/mile)
  
  ENGINE  PROP  COUPE    AVG     CRUISE  TIAS    TAS   MAX   IAS     TAS
 TYPE   SIZE  MODEL EFFICIENCY  RPM   SEA LVL 5000'  RPM  SEA LVL 5000'
 
C-75    7351   C-D      97      2275   106     114   2275  106     114
 
C-85    7150  CD-to-G   95      2400   108     116   2575  116     125
 
C-90    7152  F1-F1A    95      2350   110     118   2475  116     125
 
C-90    7153  A2-A2A    97      2350   114     123   2475  120     129
 
O-200   6950   D-G      91      2500   108     116   2750  118     127

These are the best table I've seen.  Ed

Prop related;

I normally don't send out notes like this, but if any of you are looking for a great propeller shop, please call Paul Burrows at Aero Propeller Co., Inc.  They are located immediately adjacent to Hemet Airport (HMT) and their phone number is 951 765 3178, fax: 951 765 3179.  Dave Klages

"Airport buddies say it should climb out at redline, 2575 RPM." Simple answer; “Wrong”.

The angle of incidence with the relative wind decreases on a fixed pitch prop as airspeed increases, hence the load on the engine gets less the fastyer you go. If your climb RPM is redline you could not cruise any faster than your climb speed without overspeeding the engine.

There’s been a lot of talk recently about prop pitch numbers.  Here’s my soapbox take on the subject.

There are a number of different type aircraft with C85 engines and similar speed and drag characteristics. Ercoupes, Cessna 120/140, Luscombe, Taylorcraft, the list goes on.  With the exception of the Ercoupe, they all call for a 7148 as the standard prop.  There is no reason why the Ercoupe would be any different.  Ed often refers to his “extreme climb prop”, a 7146.  For any other type, this is simply a climb prop. 7144 is extreme, or a seaplane prop.  The 7150, Ercoupe’s “standard” prop is a cruise prop in anyone else’s world.  Now, if the Ercoupe had significantly less drag (and consequently higher cruise speed) then a higher pitch might be warranted, but…

My take is that someone at Erco was very optimistic, maybe a marketing type. 

This explains the common complaint of anemic climb performance.  What do you expect with a cruise prop?  (Calling is “standard” doesn’t alter the laws of physics.
Climbing down off the soap box… John Cooper Skyport Services

>>Very interesting & informative!!!, "Emergency turn-arounds"; 

http://www.aerobats.com/seminar_02-07.html 

Great advice for emergency loss of control recovery (in the clouds);
To really keep it simple, forget about the altimeter, at least until the plane is under complete control.  Airspeed is the primary instrument for pitch.  You can be nose high and descending. Raising the nose is the WRONG response.  Center the needle (and ball) first, then, if your airspeed is below the appropriate airspeed for your power setting, lower the nose. If it's above, raise the nose.  Then you can worry about your altitude.

This procedure will work, with no outside visual reference, even if you are in a spin. - John Cooper

Humor from the Ercoupe Tech list;
Q; I have been unable to find takeoff performance chart for 415C. I need takeoff distance for 6000 at 80 deg for example.
A; According to the climb performance charts that I have, if you take off from an airport at 6000 feet MSL on an 80 deg day, you should be at 50 feet AGL by Tuesday.  Wednesday at the latest.   ;>)    Wayne DelRossi     Alon N5618F

For Ercoupe stall speeds, please see Hartmut Beil's spreadsheet @
http://ercoupe.info/index.php/Main/StallSpeeds

Ed Burkhead provided a link to information regarding cross wind landings, that is worth a close look!!!    http://edburkhead.com/Ercoupe/coupe_flying.htm
http://edburkhead.com/Ercoupe/coupe_landings.htm

This should make a good starting point for your own Ercoupes performance figures.
Depends on temperature and altitude. 
From the Ercoupe 415-D Flight Manual, at 1400 lbs,
the table to clear 50 ft for PAVED runway is as follows. 

Disclaimer, for the lawyers: Not responsible for errors in the table above... Eliacim

***Several SoCal Ercoupers have asked about best glide speed for their Ercoupes. 

Here's a link from Ed Burkhead that is very useful.   http://edburkhead.com/Ercoupe/glide_ratio_testing_procedure.htm "Till you get that done, I’d suggest the best glide ratios are in the 75-85 mph range.  EB" 

Ed Burkhead has placed some Ercoupe climb and glide performance data on his web site, based (so far) on data provided by Kim Blackseth.  While very preliminary, the glide performance is quite interesting and not necessarily what you would expect.  In this case more data would be helpful (hint hint).  You can also read some of Ed's comments about this subject.  Be sure to take a look at the numbers @ http://edburkhead.com/Ercoupe/performance_information.htm  

 An assortment of altitude, airspeed, outside air temp, and altitude combinations at idle, specific rpm and full power could be useful.  Also, list your aircraft model (it especially makes a difference whether you have an Ercoupe shaped canopy or Alon.

 Also, to properly simulate the glide behavior, it’d be very good to have some real glide testing information.  Heck, we’ve debated that for, literally, decades.  I don’t have a Coupe right now (nor a medical that would let me fly it) so I can’t go out and re-test it myself.  We could use accurate information from several people.  If you’d like some test pilot experience, there’s a procedure for glide ratio testing here:  http://edburkhead.com/Ercoupe/glide_ratio_testing_procedure.htm

Ed Burkhead writes this in response to an emergency procedures question;

As a rule of thumb, in a Coupe I’d use 1.4 times minimum flying speed for “best glide” until you can do actual testing.  Erring on the faster side won’t decrease your glide ratio much and, with a strong head wind, might even let you penetrate a bit farther.  Speeds lower than that will result in decreasing, and even radically decreasing glide ratio.  The Coupe wing has a fairly wide, flat top to the glide ratio curve as I measured it, with gentle fall off on the fast side but steep fall of on the slow side.

But, I urge everyone to do glide testing in their own Coupe and report the results to us all.  Firm numbers are scarce.  Suggested glide ratio testing procedure: http://edburkhead.com/Ercoupe/glide_ratio_testing_procedure.htm

***Walt Wasowski (CFI) shares these useful insights about his experience with Ercoupe glide range (Excel spreadsheet is attached for reference); "Here is the EXCEL spreadsheet for the glide distance and estimating distance over the nose.  Estimate the height above the ground by looking at your chart and subtract it from your altitude.  Then read the glide distance in nautical miles.  The Ercoupe glide approximately 1.6 NM per 1000 feet AGL.  Estimating the distance over the nose is done the same way.  Find the distance above the ground then punch the graph to find the distance in nautical miles, Distance you see looking over the nose is approximately 2.0 NM per 1000 feet AGL."  Walt    (The same comments apply here; your planes glide performance may differ, so be sure to safely confirm your planes performance for yourself!  Dan)

Walt forwards great set of excel tables for best glide.   Click on the link to DOWNLOAD the spreadsheet to your computer.  Then open the file with Excel. 

***Mike Willis (our recent visitor from the UK) mentions a potential option that is probably as good a starting point for Ercoupe (ALON!) performance as any.

The Flight Manual for my Alon A2, published by Univair (part no. LFM).  I see from their listing that there is also one for the 415D part no. DFM.
My flight manual states at the front:  “Note: The FAA did not require Alon to develop a Flight Manual for this aircraft.  There is no Flight Manual required on the Alon’s Type Design Data Sheet A-787.  This manual was published by Alon for the UK Civil Aviation Administration for certification in the UK.  However, the information contained is useful to Alon owners.”  My thinking is therefore that you US guys may not be aware of it’s existence.

The Flight Manual has lots of interesting performance charts, like take-off run and distance required, net gradient of climb, performance ceiling, en-route glide (never heard it called that before, but maybe a good thing to say to your passenger rather than ‘oh sh#t the engine’s failed!).  All these for different take-off weights, temps and pressures.  There is also a position error correction to ASI.  It assumes an Alon A2, C90 and 7150 prop.

I’m not suggesting for one minute that you shouldn’t do your own measurements, but I haven’t heard of any ‘official’ figures mentioned in this discussion so thought I’d bring them up.

***Re: [COUPERS] Coupe airfoil Date: Thu, 15 Jun 2000 19:11:25

The airfoil is 43013.  The only other aircraft to use the 43000 family of airfoils is the ATR-42/72 air carrier turboprops.

The airfoil is constructed by taking a symmetrical airfoil and bending the leading edge down at the 15% point to form a 13% camber.  The airfoil achieves good low drag performance in cruise as would a symmetrical airfoil and develops good lift coefficients at high angles of attack because of the drooped leading edge.  The airfoil has very little pitching moment which lowers the trim drag, further reducing drag.

The bad news is that the airfoil has a big problem with stall recovery and must only be used in aircraft which are never allowed to stall.  The problem is that once stalled, the wing will not un-stall until a significantly greater than stall speed is achieved.  This would be considered undesirable in a trainer or any service where good slow flight behavior is important.

The unpleasant behavior of this series of airfoils worries me when someone suggests trying to modify and improve the wing with vortex generators and wing tip mods.  This is an area to move very slowly in and,  there are more productive ways to improve performance.

The five digit airfoils were very popular with NACA at the time of the Ercoupes' development but they are easily improved upon by the six digit airfoil series.  When the Ercoupe was reincarnated as the Cherokee series a six digit airfoil was chosen even though the wing could not be constructed smoothly enough to achieve the benefits of laminar airflow.  The more common of the five digit airfoils are the 23000 series which are very common on light twins and some singles although the airfoil shares the poor stall behavior of the 43000 series.  When you hear of a light twin loosing control and rolling inverted after the failure of one engine, the airfoil is a big contributor to the event.

Is this more than you wanted to know about your wing? Good luck, Bob Condon

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Last modified: 07/09/10