TIGHAR
Amelia Earhart Search Forum => Aircraft & Powerplant, Performance and Operations => Topic started by: Martin X. Moleski, SJ on October 07, 2009, 11:20:51 AM
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New report by C.L. Johnson (June 4, 1936) (http://tighar.org/Projects/Earhart/Documents/Report_487/Report487.pdf) up on the website.
Required reading for anyone who wants to estimate the aircraft's theoretical range.
Beautifully done--37 pages!
Marty
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Marty,
You are right this is well done. Is a scan of the original available? Having been using old aerospace engineering reports for some time I don't readily trust transcriptions! It is too easy to make a mistake!
Jay
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You are right this is well done. Is a scan of the original available?
Not that I know of.
All that Pat said (http://tighar.org/Projects/Earhart/Documents/Report_487/Report487.html) was that the transcription came from a microfilm.
Having been using old aerospace engineering reports for some time I don't readily trust transcriptions! It is too easy to make a mistake!
If you see something that looks wrong, you could ask about it. Politely. I'm not sure how the transcription was made. I've been pleasantly surprised by some recent things I did with Optical Character Recognition.
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Marty,
No. I'm just curious. The graphs just looked a little too clean!
I guess I've been burned one too many times with transcribed data! I have to be care or the old curmudgeon engineer starts to come out!
Thanks for the quick reply!
Jay
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No. I'm just curious. The graphs just looked a little too clean!
Understood. I don't know how Pat produced them. They are a work of art!
I guess I've been burned one too many times with transcribed data! I have to be careful or the old curmudgeon engineer starts to come out!
The concept of "reasonable doubt" suggests that there may also be "unreasonable doubt."
My guess is that Pat faithfully reproduced the graphs as published by Lockheed. I presume that the new charts look a lot like the old--and are not data sets plotted from experiments but theoretic curves that give a general idea of performance. That they are "too clean to be true" is not Pat's fault but Lockheed's.
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Lockheed Report 487, June 4. 1936, is a very thorough and well written technical report. In addition to the assessment that report 487 is merely a marketing document, it is also a procedural guide that contains numerous recommendations for operation of the 10E. It is very similar to operations and specifications manuals that I have had to study and master over the years while transitioning into larger and more complex aircraft.
In regards to range and fuel consumption, the argument advanced that Earhart used excessive fuel en route to the LOP because the Cambridge Exhaust Gas Analyzer malfunctioned, is not convincing. The evidence put forth to support that claim is very lame and does not even rise to the level of circumstantial.
The apparent function of the instrument was to enable the pilot to precisely lean the fuel mixture for each engine. Specific Cambridge settings were calculated by Lockheed and provided to Earhart. Notwithstanding, she should have been able to lean the mixture without the instrument and if failure of the instrument did occur, she surely would not have ignored the leaning procedure.
Lockheed Report 487, Model 10E, page 3, specifies “Watch the mixture closely at all times. The engines must be run very lean,” “in climb when the power output is increased, check the mixture,“ and on page 5 and page 9, “WATCH MIXTURE AT ALL TIMES”.
Most of my flying has been with turbine engines but I do recall that in flight school while flying with piston engines, we were taught how and when to lean the fuel mixture by observing the RPM. If you lose instruments, either attitude or engine instruments, there are always options. Maybe in 1937, this was not the case.
In regards to the report by Earhart that she was flying at 1000’ altitude when on approach to Howland, not only was this so she could see the island, this let down procedure is specified in Lockheed Report 487, page 3, “When about 100 to 150 miles from the end of the flight, put the ship in a power glide losing about 250 to 300 feet of altitude per minutes while maintaining cruising power output.”
The fact that it appears that Earhart may have been trying to follow the procedures and recommendations of the manufacturer in this complex and technical report, indicates that perhaps, other than radio procedures, she might have been more astute in her approach to flying the aircraft than she has been given credit for. Perhaps not!
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Very intersting! Thanks for sharing the link, Marty! :)
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... The fact that it appears that Earhart may have been trying to follow the procedures and recommendations of the manufacturer in this complex and technical report, indicates that perhaps, other than radio procedures, she might have been more astute in her approach to flying the aircraft than she has been given credit for. ...
After the disaster at Luke Field (http://tighar.org/wiki/Luke_Field), which certainly calls her abilities and judgment into question, AE flew 29 legs of her journey around the world (http://tighar.org/wiki/Timeline) without further mishap.
Her takeoff from Lae was masterful and took a huge amount of courage. AE stayed calm while the plane descended from the bluff at the end of the runway back into ground effect. She held steady at low altitude until the plane disappeared in the distance and eventually got up to her planned cruising altitude. If even one of the post-loss radio messages is real, that means that she brought the plane down safely on her last flight.
If courage and stick-and-rudder skills were all that were needed to complete the journey, she would have made it.
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In regards to range and fuel consumption, the argument advanced that Earhart used excessive fuel en route to the LOP because the Cambridge Exhaust Gas Analyzer malfunctioned, is not convincing. The evidence put forth to support that claim is very lame and does not even rise to the level of circumstantial.
The apparent function of the instrument was to enable the pilot to precisely lean the fuel mixture for each engine. Specific Cambridge settings were calculated by Lockheed and provided to Earhart. Notwithstanding, she should have been able to lean the mixture without the instrument and if failure of the instrument did occur, she surely would not have ignored the leaning procedure.
Good point. I agree completely.
Following procedures would have provided nearly the same exact results as the instrument. After all, that's how procedures are derived in the first place - from instruments like this. Instruments are simply redundant backups to make sure procedures are being followed correctly.
One could even argue that because of the instrument failure, she would have paid even more attention to the proper procedures.
In other words, the instrument failure itself is not a convincing argument without evidence that AE also failed to follow procedures. I would say that she was keenly aware of the consequences resulting from not properly leaning the engines. Which adds more credence that she would not have ignored those procedures. Engine temps would certainly have been one good clue. Even with her past mistakes, it's hard for me to buy that argument. Possible - Yes, Probable - No.
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All,
It would be interesting to visit the flight profile of AE’s around the world flight and compare that to the Johnson report as what to do.
We know the distance, time, and target airport on each leg. We also have some (maybe all up to the final refueling) how much fuel she put on board for each leg. A little mathematics should show whether or not AE was following the recommendations of Johnson or was she winging it.
Ted Campbell
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> ... We also have some (maybe all up to the final refueling) how much fuel she put on board for each leg. ...
That doesn't ring a bell. Have you got a link to that data?
We do have the distance for each leg (http://tighar.org/wiki/Timeline). It may be a theoretical distance derived from maps rather than actual distance made good on the flight, which could introduce some errors into the calculations.
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Montaro Product Development Services modeled the performance of the Electra 10E using the Kelly Johnson and W. C. Nelson 1936 report. They also reference TIGHAR in the intro. Here is a link to the pdf of their report. Don't know if their model is available for use by others.
http://www.mantaro.com/downloads/Electra_10E_Model_Amelia_Earhart.pdf
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Montaro Product Development Services modeled the performance of the Electra 10E using the Kelly Johnson and W. C. Nelson 1936 report. They also reference TIGHAR in the intro. Here is a link to the pdf of their report. Don't know if their model is available for use by others.
http://www.mantaro.com/downloads/Electra_10E_Model_Amelia_Earhart.pdf
Thanks for the link, Robert. I think I met David and saw a demo of the simulator. We talked a little bit about how to do a web-accessible version. That was a few years ago, I believe.
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What a great find. Thanks for all the great resources, Ric--and everyone associated with this site (and cite!). The Kelly/Nelson document is certainly a valuable piece of historical info.
The first thing that jumped out at me was the typo in the HP required column, p.30--min. gross wt. That was an eyebrow raiser. I thought at first it was sloppy work from Kelly and Nelson, but reading this thread, I suspect it arose when the document was transferred from microfilm into Adobe.
Some other comments:
"Complete data on the fuel consumption of the engine was not available so generalized data on aircooled engines was used. (see pg. )"
Report 487, p. 20.
Wow! That's one hell of a qualification to bet your life on! Especially since Johnson predicts the big improvement in specific range doesn't occur until 9+ hours into max range flight (see my little spreadsheet attached).
I’ve spent paid time in the left seat out over that ocean that makes the Atlantic seem like a river. If we’re talking flying the Pacific in our L10E, that puts it around our point of no return, assuming a) we’re smart enough to realize we have one, b) we’ve bothered to figure out where it is, and c) we know what we should check before we go through that particular one-way door. What happens if we’re on the other side when we discover we can’t get our gallons per hour down below 40? What are we going to do then, swim back to Burbank to complain? ;-)
The only mention of actual fuel consumption achieved in AE’s Electra that I’ve found refers to the first attempt Oakland-Honolulu segment. It’s in the posthumous book Last Flight that GP put together from her surviving notes:
“Daylight comes at last. The stars fade. We are throttled down to 120 indicated airspeed so as not to arrive in darkness. We are burning less than 20 gallons of gas at 10,000 feet.” (p.37)
She’s surprised they’re burning less than 20gph/engine! Doesn’t she know she has to get 19 at full throttle for 10+ hours for max range flight?? Not throttled back at 120 IAS with Mantz in the right seat to handle the mixture?? That’s what the remainder line in Johnson’s March 11 telegram calls for.
Maybe she just bought this flat-footed conclusion by the greatest aeronautical engineer of all time:
"(1). It is possible to fly a Lockheed Electra Model 10E non–stop for a distance between 4100 and 4500 miles starting out with 1200 gallons of gasoline and the proper amount of oil."
She certainly never seems to have bothered to do this:
"(3). The Cambridge Gas Analyzers should be carefully calibrated in flight to see if the fuel consumption data used in this analysis can be obtained. This should be done before attempting any long range flight."
What's the max range anybody ever flew an L10E and lived to tell the tale? Any record out there?
I just wonder how many of Kelly’s 4,100 to 4,500 miles were on marketing fumes.
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"(1). It is possible to fly a Lockheed Electra Model 10E non–stop for a distance between 4100 and 4500 miles starting out with 1200 gallons of gasoline and the proper amount of oil."
She certainly never seems to have bothered to do this:
"(3). The Cambridge Gas Analyzers should be carefully calibrated in flight to see if the fuel consumption data used in this analysis can be obtained. This should be done before attempting any long range flight."
What's the max range anybody ever flew an L10E and lived to tell the tale? Any record out there?
I just wonder how many of Kelly’s 4,100 to 4,500 miles were on marketing fumes.
When we look at the published maximum range of any aircraft today, it will be based on a 'ferry' flight with ideal conditions, minimum load and maximum fuel and will include landing with enough fuel remaining for a 'VFR' or 'IFR' Reserve Fuel remaining or even a 'NBAA' calculation to include a diversion to an alternate, plus a reserve.
In 1937; the "It is possible to fly..." range statement meant to dry tanks under ideal conditions and you were expected to subtract your landing reserves and diversion to alternate from that number. Otherwise you would most certainly be running on "Marketing Fumes" :)
Prior to Amelia's unfortunate last flight; in May 1937, H.T. "Dick" Merrill and J.S. Lambie accomplished a round-trip crossing of the Atlantic Ocean; this feat was declared the first round-trip commercial crossing of that ocean, and it won them the Harmon Trophy. On the eastbound trip, they carried photographs of the crash of the Hindenburg, and on the return trip, they brought photographs of the coronation of King George VI.
They also flew a Lockheed 10E and theirs was probably the only other "Special" version produced by Lockheed with all those huge ferry tanks installed and higher gross weight allowed. Those 3,465 Statute Mile Great Circle Routes no-doubt proved that the Lockheed 10E Special had the range needed for Amelia's Flight Plans (even including a diversion to Gardner Island).
It is ironic how Amelia, due to her tragic and completely avoidable loss is exceeded in fame only by Lindbergh and the Wright Brothers, way ahead of Doolittle, Merrill, Rickenbacker and so many other far more notable Aviators.
Merrill was also featured in a 1937 Film "Atlantic Flight' based on and with footage from his Lockheed Trans-Atlantic Flights.
Merrill had previously (September 1936) crossed the Atlantic, 'First Round-Trip'; in a single engine Vultee V1A (with millionaire singer Harry Richman, famed for Puttin' on the Ritz), this had been the "Ping-Pong" flight. In modifying the Vultee for the trip, the most modern equipment was sought out by Merrill, including the Hooven Radio Direction Finder (licensed to Bendix). It was Richman's idea to fill empty spaces in the wings and fuselage with 41,000 ping pong balls, which it was hoped would allow the aircraft to float if it was forced down in the ocean.
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Thanks for the info, Art. And Happy New Year!
I googled the Merrill/Lambie L10e flight and found this clip:
http://www.time.com/time/magazine/article/0,9171,848691,00.html
Funny I just saw the actual film of the coronation this week--in the film THE KINGS SPEECH, which I thought was great. The older I get, the more everything seems related. Anyway, it certainly looks like Merrill refueled in MA before proceeding on. Do we know if that's in fact the case?
That's still a respectable 3,100sm or so from the UK. And we can keep wind out of it if we concentrate on hours at max range. Merrill knew what he was doing, without doubt. I figure 190sm from Squantum Point to Floyd Bennett. When did these guys make the decision to land in Quincy? If I figure it took 2.5 hours to land, refuel, takeoff and fly to Brooklyn and subtract that from their total flight time of 24 hrs 22 min., that tells me these guys were low fuel less than 22 hours into the flight. Otherwise, why not fly on (reasonably safely) overland to Brooklyn? Kelly's not looking so good with his 4,100-4,500. And if Merrill's low fuel at 22 hours of max range flight, all AE has to be is 10% less efficient, and she's low fuel at 20.
One thing puzzles me. My multiengine prop time is limited to 1/2 hour in the right seat of a DC-3 that was older than I was. But I remember enough aerodynamics to recall that max range in a prop = max endurance in a jet. It's L/D max. Where's the mention of angle of attack in Kelly's notes trying to sell the L10e? He does call for a step climb, but the optimum procedure would be to set the angle of attack, throttle (max) and your mixture and take what altitude it gave you, i.e., a gradual climb as your fuel burned down.
Did Johnson ever say anything afterwards about the AE flight?
Again, thanks for gathering all this great info in one place. I'm not trying to rain on anybody's parade, just fascinated.
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Found another tidbit on the Merrill/Lambie flight. According to Long (p.124-5), when they met Earhart in Miami, they told her "that coming back from England they stayed low over the water at 1,500 feet. They maintained a constant indicated airspeed of 135mph, and after all corrections had averaged a true airspeed of 140 mph. Merrill believed the 1,270 gallons of fuel onboard when he took off from England could have kept them going for at least 26 hours."
Long cites Jack King's WINGS OF MAN as his source for this.
If we take Collopy's 1,100 gallons of fuel onboard at takeoff from Lae, that means Merrill and Lambie had 170 gallons more than Earhart. At Kelly Johnson's "remainder" line of 39gph, that's 4+ hours more flight time at max specific range. 26-4=22 hours of max range flight, and that without hauling all that fuel up to 10,000 feet, which Earhart had by at least 0519Z. The more I look at this, the worse Kelly Johnson and the boys at Lockheed look to me with their promised range for this bird.
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If we take Collopy's 1,100 gallons of fuel onboard at takeoff from Lae, that means Merrill and Lambie had 170 gallons more than Earhart. At Kelly Johnson's "remainder" line of 39gph, that's 4+ hours more flight time at max specific range. 26-4=22 hours of max range flight, and that without hauling all that fuel up to 10,000 feet, which Earhart had by at least 0519Z. The more I look at this, the worse Kelly Johnson and the boys at Lockheed look to me with their promised range for this bird.
I'm confused. If Earhart was flying at 10,000 ft., isn't flying at a higher altitude BETTER for fuel efficiency? I think I'm missing something here.
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As I've indicated, I'm not much of a prop jock, Nancy. And if you're riding a turbine, whether it's hooked to a prop or not, you're right--keep climbing as long as the OAT is going down. But that's not the case with an air pump like a recip. If the throttle isn't wide open, the cylinder has to suck harder to get air into it. That sucking takes energy away from shaft driving the prop, so you burn more gas. Altitude isn't nearly as important in a prop as throttle setting and mixture. This is a cool site where you can play with the variables:
http://selair.selkirk.ca/Training/Aerodynamics/range_prop.htm
Here are some quotes. Specific range is miles per gallon or lb. of fuel:
"Effect of Altitude on Specific Range and Endurance
Previously we saw that altitude had a huge effect on SR for jet airplanes. But it actually has almost no effect on propeller airplanes.
As the drag curve shifts to the right with altitude the power curve shifts up because power drag x velocity (and shifting to the right represents an increase in velocity even though drag does not change.)
How does altitude affect endurance of a propeller airplane?
In the graph to the left you can see the bottom of the FF curve moves UP with altitude. Therefore maximum endurance occurs at sea level for a propeller airplane.
Of course this does not take changes in SFC that occur with altitude into account. Previously we saw that altitude has only a minor effect on piston engines, so we expect a piston airplane to achieve maximum endurance at or very close to sea level.
NOTE: piston engines are usually manually leaned while jet and turboprop engine fuel flows are electronically controlled. The pilot is the most likely culprit causing high SFC for piston engines. If the pilot does not properly lean the engine then everything said below is completely invalid.
How does altitude affect the Range of a propeller airplane?
The graph to the left shows that SR does not change with altitude. Recall from above that SR is maximum when the angle "R" is minimum. You can see that R does not change with altitude, therefore SR does not change.
As with the discussion of endurance, this analysis assumes that altitude does not affect SFC. We know that for a piston airplane altitude has no substantial effect on SFC although we should fly high enough to operate at full throttle. This leads to the conclusion that piston airplanes achieve maximum - or the same - range at any altitude from about 6000 or higher.
The most important point, and one that cannot be emphasized too much is that the main factor determining cruise altitude for a propeller airplane is wind. On most days wind gets stronger with altitude so it would be foolish to climb into a stronger headwind given the graph for range shown above. It would be equally foolish NOT to climb if a stronger tailwind is available. Pilots who do not heed this advice are being wasteful with fuel.
On days when the wind is light any altitude will do, but it is IMPORTANT to note that while the airplane achieves the same SR at all altitudes, TAS increases with altitude. In other words you will get to your destination faster at higher altitude. Since the old saying that time is money is pretty close to being true where airplanes are concerned it "pays" to fly higher. It does NOT pay in fuel, but it does pay in other ways."
Me again: Per Chater, the Nauru weather observation, received as Earhart was taking off, included the following: "NARU 8 AM UPPER AIR OBSERVATION 2000 FEET 90 DEGREES 14 MPH 4000 FEET 90 DEGREES 12 MPH 7500 FEET 90 DEGREES 24 MPH."
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...I googled the Merrill/Lambie L10e flight and found this clip:
http://www.time.com/time/magazine/article/0,9171,848691,00.html
...When did these guys make the decision to land in Quincy? If I figure it took 2.5 hours to land, refuel, takeoff and fly to Brooklyn and subtract that from their total flight time of 24 hrs 22 min., that tells me these guys were low fuel less than 22 hours into the flight.
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According to "Wings of Man," they were on the ground at Squantum for only 20 minutes and they did not take on any fuel, they made up the story about a fuel concern to cover up that they didn't know where they were and had landed just to find out.
gl
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Are the Engine power curves, pages 17 and 18, available, even poor copies that have not been cleaned up?
Richard Cooke
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Are the Engine power curves, pages 17 and 18, available, even poor copies that have not been cleaned up?
The introduction to "Lockheed Report 487 (http://tighar.org/Projects/Earhart/Archives/Documents/Report_487/Report487.html)" says that those pages were not on the microfilm containing the rest of the report.
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Are the Engine power curves, pages 17 and 18, available, even poor copies that have not been cleaned up?
The introduction to "Lockheed Report 487 (http://tighar.org/Projects/Earhart/Archives/Documents/Report_487/Report487.html)" says that those pages were not on the microfilm containing the rest of the report.
Thanks I had noticed that but hoped they, or something equivalent, might have been discovered in the last couple of years.
I'm wading through the archives and found a reference to a Lockheed test report 465 on an Electra 10E. Is that report available to us?
As a newbie here I risk asking things that have been asked before but I have one thing that intrigues me namely has someone noticed that the conservative profile in L487 would cover 2560 miles in 16.1 hours giving a 159mph ground speed? This high speed is obviously because you have to fly faster at the start of the profile when the plane is heavy.
Thanks
Richard Cooke
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Are the Engine power curves, pages 17 and 18, available, even poor copies that have not been cleaned up?
The introduction to "Lockheed Report 487 (http://tighar.org/Projects/Earhart/Archives/Documents/Report_487/Report487.html)" says that those pages were not on the microfilm containing the rest of the report.
Thanks I had noticed that but hoped they, or something equivalent, might have been discovered in the last couple of years.
If that was what you meant to ask, you phrased your question poorly. You made it sound as though you had not read the introduction to the report.
I'm wading through the archives and found a reference to a Lockheed test report 465 on an Electra 10E. Is that report available to us?
You can answer that question by learning how to find things on the TIGHAR website (http://tighar.org/smf/index.php/topic,454.0.html). I'm especially fond of the search page (http://tighar.org/news/help/82-how-do-i-search-tigharorg). It is also possible to use any Google search field (http://tighar.org/smf/lmgtfy.com/?q=site%3Atighar.org+Lockheed+test+report+465) in your browser to search tighar.org.
As a newbie here I risk asking things that have been asked before but I have one thing that intrigues me namely has someone noticed that the conservative profile in L487 would cover 2560 miles in 16.1 hours giving a 159mph ground speed?
As an eleven-year veteran of the Forum, I say, "Yes, someone has noticed."
This high speed is obviously because you have to fly faster at the start of the profile when the plane is heavy.
That does not sound obvious or correct to me.
It takes more power to fly at the target speed with a heavy fuel load.
It takes more power to climb to the target cruising altitude with a heavy fuel load.
The plane therefore burns more fuel early on than it does later in the flight.
It does not necessarily go faster earlier and slower later.
Even if your observation were correct, I don't see what difference it would make in TIGHAR's evaluation of what might have happened to the aircraft and crew.
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Just to add a bit of extra background info here is the NACA test report from which L487 got its prop data.
Interestingly the report tests the effect of reducing the diameter of a 10ft design by cutting off the blade ends. Lockheed used the data for the one cut down to 9 ft with a consequent reduction in peak efficiency from 83.5 to 81%. It's fascinating to wonder if a cut down 10ft prop was fitted to Lockheed 10Es, or was it the only data they had for 9ft props.
I cant tell from any photographs if NR16020 had a prop which was designed to be 9ft, or a 10ft prop cut down to 9ft, which would have stubby blade ends. If it had a genuine 9ft design then the extra 2.5% efficiency over L487, would have made the "ran out of fuel" theory even less likely.
Richard Cooke
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VERY interesting prospect, Richard, and a good find. I look forward to digging into this data. It really could tell us more about NR16020's real capabilities if we can sort out the prop mystery, although I have taken the Lockheed report at face value regarding the assumptions there (meaning if they took data from the NACA report and applied it to the hardware, that's what should have been on the ship).
LTM -
Jeff
I would hope they fitted something better, because this NACA report was written in 1929 so they were testing a normal blade shape and profile of that year. The equivalent tests from 1937, with shape and profile refinements, have peak efficiency at 86/87% so a much better prop was available.
In the TIGHAR archives there are several references to Lockheed test report 465, which has flight test data for a standard Electra 10E, but I have failed to find the actual report. With flight test data of a standard 10E, the data in L487, and what is now known about the weight it would be quite easy to calculate what NR16020 should have been capable of.
For anyone is interested in NACA test reports here is the url to the site where I get them from:
http://naca.central.cranfield.ac.uk/
Richard Cooke
PS there seem to be 7640 reports so it might a lot of spare time to read them ;D
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VERY interesting prospect, Richard, and a good find. I look forward to digging into this data. It really could tell us more about NR16020's real capabilities if we can sort out the prop mystery, although I have taken the Lockheed report at face value regarding the assumptions there (meaning if they took data from the NACA report and applied it to the hardware, that's what should have been on the ship).
LTM -
Jeff
I would hope they fitted something better, because this NACA report was written in 1929 so they were testing a normal blade shape and profile of that year. The equivalent tests from 1937, with shape and profile refinements, have peak efficiency at 86/87% so a much better prop was available.
In the TIGHAR archives there are several references to Lockheed test report 465, which has flight test data for a standard Electra 10E, but I have failed to find the actual report. With flight test data of a standard 10E, the data in L487, and what is now known about the weight it would be quite easy to calculate what NR16020 should have been capable of.
For anyone is interested in NACA test reports here is the url to the site where I get them from:
http://naca.central.cranfield.ac.uk/
Richard Cooke
PS there seem to be 7640 reports so it might a lot of spare time to read them ;D
If you look at the graph on page 25 and the tables on pages 31 though 33 of report 487 you will find the highest prop efficiency is 79%
gl
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The graph on page 25 for 28deg just gets over 80%, but as you noticed none of the points used for the flight profile reach that, and many are significantly lower. The prop was a good choice to give the standard 10E the best top speed, but was less than optimum for EA's low power and low speed requirement.
RC