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Author Topic: Lockheed Report 487 on the Electra's range and speed  (Read 27483 times)

Mike Colleran

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Re: Lockheed Report 487 on the Electra's range and speed
« Reply #15 on: January 01, 2011, 09:56:47 PM »

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.
« Last Edit: January 02, 2011, 01:06:17 AM by Mike Colleran »
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Mike Colleran

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Re: Lockheed Report 487 on the Electra's range and speed
« Reply #16 on: January 27, 2011, 02:26:39 PM »

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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Nancy Marilyn Gould

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Re: Lockheed Report 487 on the Electra's range and speed
« Reply #17 on: January 27, 2011, 07:36:04 PM »

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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Mike Colleran

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Re: Lockheed Report 487 on the Electra's range and speed
« Reply #18 on: January 27, 2011, 08:45:25 PM »

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."


 
« Last Edit: January 27, 2011, 08:47:11 PM by Mike Colleran »
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Gary LaPook

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Re: Lockheed Report 487 on the Electra's range and speed
« Reply #19 on: August 28, 2011, 08:18:30 PM »

...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. 
-------------------------


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
« Last Edit: July 16, 2012, 02:22:21 PM by J. Nevill »
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Richard C Cooke

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Re: Lockheed Report 487 on the Electra's range and speed
« Reply #20 on: November 20, 2011, 11:56:23 AM »

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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Martin X. Moleski, SJ

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Re: Lockheed Report 487 on the Electra's range and speed
« Reply #21 on: November 20, 2011, 09:58:36 PM »

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" says that those pages were not on the microfilm containing the rest of the report.
LTM,

           Marty
           TIGHAR #2359A
 
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Richard C Cooke

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Re: Lockheed Report 487 on the Electra's range and speed
« Reply #22 on: November 23, 2011, 05:53:02 AM »

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" 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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Martin X. Moleski, SJ

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Re: Lockheed Report 487 on the Electra's range and speed
« Reply #23 on: November 23, 2011, 06:54:02 AM »

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" 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.

Quote
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.  I'm especially fond of the search page.  It is also possible to use any Google search field in your browser to search tighar.org.

Quote
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."

Quote
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.
LTM,

           Marty
           TIGHAR #2359A
 
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Richard C Cooke

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Re: Lockheed Report 487 on the Electra's range and speed
« Reply #24 on: December 04, 2011, 03:41:16 PM »

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
« Last Edit: December 04, 2011, 08:24:21 PM by Richard C Cooke »
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Richard C Cooke

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Re: Lockheed Report 487 on the Electra's range and speed
« Reply #25 on: December 06, 2011, 04:30:59 PM »

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
« Last Edit: December 06, 2011, 06:06:34 PM by Richard C Cooke »
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Gary LaPook

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Re: Lockheed Report 487 on the Electra's range and speed
« Reply #26 on: December 07, 2011, 10:07:36 PM »

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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Richard C Cooke

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Re: Lockheed Report 487 on the Electra's range and speed
« Reply #27 on: December 08, 2011, 07:16:37 AM »

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
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