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Author Topic: Airworthiness Certificate(s); fuel capacity  (Read 85809 times)

Gary LaPook

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Re: Airworthiness Certificate(s); fuel capacity
« Reply #15 on: November 25, 2011, 11:23:31 AM »

Everybody,

I'm sure Gary was joking about the 'incontrovertible proof.'


---------------------

You know I just like to stimulate discussion.

gl
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Harry Howe, Jr.

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Re: Airworthiness Certificate(s); fuel capacity
« Reply #16 on: November 25, 2011, 12:16:54 PM »



It is all Quantum Mechanics (or String Theory).  There is a wave function connecting the wings and the CA that has a "1" (plane can fly) if and only if the wings and the CA are present on/in the plane.

Since the CA was in California ( in the suitcase in thhe closet) and the plane was in New Guinea, it couldn't takeoff in our dimensions so it went into that alternate universe paralelling ours where it found an alternate CA and was thus able to fly and reach its destination.

Now if we can just find that alternate Howland Island we will find the plane and AE/FN
LOL
No Worries Mates
LTM   Harry (TIGHAR #3244R)
 
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Ric Gillespie

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Re: Airworthiness Certificate(s); fuel capacity
« Reply #17 on: November 25, 2011, 12:17:36 PM »

I noticed all the points you bring up, so we agree on this.

See my explanation above.  We don't have to speculate about this.  We have the documents.

I think the discrepancy between the 100 gallons listed on the original July 1936 application for a license and the 102 gallons listed for the wing tanks is most likely a simple error since the blueprints for the fuel system lists the tanks as 102 gallons and the blueprints are dated prior to the first flight. Anyway, we can be sure that they didn't rip out the 100 gallons tanks to be replaced by 102 gallon tanks after the Luke field crash, the wings didn't sustain a lot of damage.

Strange as it seems, I think the facts argue for the actual replacement of the 100 gallon tanks with 102 gallon tanks.  The tanks were consistently listed as being 100 gallons until November 1936 and consistently listed as 102 gallons thereafter.  There is even a photo of them apparently being worked on.

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Gary LaPook

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Re: Airworthiness Certificate(s); fuel capacity
« Reply #18 on: November 25, 2011, 01:59:24 PM »

I noticed all the points you bring up, so we agree on this.

See my explanation above.  We don't have to speculate about this.  We have the documents.

I think the discrepancy between the 100 gallons listed on the original July 1936 application for a license and the 102 gallons listed for the wing tanks is most likely a simple error since the blueprints for the fuel system lists the tanks as 102 gallons and the blueprints are dated prior to the first flight. Anyway, we can be sure that they didn't rip out the 100 gallons tanks to be replaced by 102 gallon tanks after the Luke field crash, the wings didn't sustain a lot of damage.

Strange as it seems, I think the facts argue for the actual replacement of the 100 gallon tanks with 102 gallon tanks.  The tanks were consistently listed as being 100 gallons until November 1936 and consistently listed as 102 gallons thereafter.  There is even a photo of them apparently being worked on.
-------------------------------
The blueprints are dated March 12, 1937 showing the 102 gallon tanks. Since they changed the capacity prior to the crash in Hawaii we know that it wasn't a change done while the plane was being repaired. Just a guess but maybe they figured that the tanks held 100 gallons and then by actual measurement they found that they actually held 102, maybe taking the filler necks into account, its a long way from the fuel caps in the nacelles to the 102 gallon tanks behind the spars.

gl
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Bill Mangus

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Re: Airworthiness Certificate(s); fuel capacity
« Reply #19 on: November 25, 2011, 03:26:32 PM »

I found the story about finding the C of A interesting.  I wonder if anyone knows if this mechanic was one of those who worked on NR16020 after the accident at Luke Field.  Too late for an interview of course, but maybe the cache of memorabilia contains details of the repairs made that might match up with the material found on Niku.
Bill Mangus
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Ric Gillespie

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Re: Airworthiness Certificate(s); fuel capacity
« Reply #20 on: November 26, 2011, 09:22:10 AM »

It would be cool to find a stash of records on the repairs - SOMETHING must be out there somewhere... wonder who else worked for Mantz who might still have a dusty box in the attic?

We have the detailed repair orders and will put them on the TIGHAR website.  What we don't have - and probably never existed - is a record of exactly how the repairs orders were carried out. 
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Harry Howe, Jr.

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Re: Airworthiness Certificate(s); fuel capacity
« Reply #21 on: November 26, 2011, 11:20:08 AM »


Let's see, 2 tanks with 2 gallons more equals 4 gallons.  Assuming 40 gallons per hour fuel management, that represents 1/10th hour or 6 minutes which, at 133 mph represents about 13 miles.  Could be the difference between getting wet and landing on a reef.
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Gary LaPook

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Re: Airworthiness Certificate(s); fuel capacity
« Reply #22 on: November 26, 2011, 12:41:58 PM »

I noticed all the points you bring up, so we agree on this.

See my explanation above.  We don't have to speculate about this.  We have the documents.

I think the discrepancy between the 100 gallons listed on the original July 1936 application for a license and the 102 gallons listed for the wing tanks is most likely a simple error since the blueprints for the fuel system lists the tanks as 102 gallons and the blueprints are dated prior to the first flight. Anyway, we can be sure that they didn't rip out the 100 gallons tanks to be replaced by 102 gallon tanks after the Luke field crash, the wings didn't sustain a lot of damage.

Strange as it seems, I think the facts argue for the actual replacement of the 100 gallon tanks with 102 gallon tanks.  The tanks were consistently listed as being 100 gallons until November 1936 and consistently listed as 102 gallons thereafter.  There is even a photo of them apparently being worked on.
-------------------------------
The blueprints are dated March 12, 1937 showing the 102 gallon tanks. Since they changed the capacity prior to the crash in Hawaii we know that it wasn't a change done while the plane was being repaired. Just a guess but maybe they figured that the tanks held 100 gallons and then by actual measurement they found that they actually held 102, maybe taking the filler necks into account, its a long way from the fuel caps in the nacelles to the 102 gallon tanks behind the spars.

gl

I have a hunch you are right, Gary. 

 I agree.

From the point of view of going anal to add that little tad of fuel, it would have been far more productive to lash a 5 gallon jerry can down in the cabin.



LTM -
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I was going to say that, too.

gl
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Don Dollinger

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Re: Airworthiness Certificate(s); fuel capacity
« Reply #23 on: November 29, 2011, 12:01:17 PM »

Quote
It is all Quantum Mechanics (or String Theory).  There is a wave function connecting the wings and the CA that has a "1" (plane can fly) if and only if the wings and the CA are present on/in the plane.

Since the CA was in California ( in the suitcase in thhe closet) and the plane was in New Guinea, it couldn't takeoff in our dimensions so it went into that alternate universe paralelling ours where it found an alternate CA and was thus able to fly and reach its destination.

Now if we can just find that alternate Howland Island we will find the plane and AE/FN

So, are you saying that the Star Trek AE episode was actually a Documentary?

LTM,

Don
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Gary LaPook

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Re: Airworthiness Certificate(s); fuel capacity
« Reply #24 on: November 29, 2011, 10:58:39 PM »


The additional 243 lbs could possibly have affected the takeoff roll and since she had 1110.5 gallons and plenty of range (endurance) for the proposed leg it was probably prudent to go without the 40.5 gallons.  I might have considered gassing up and leaving Fred behind.  MHO

Lockheed report 487, page 2, shows the takeoff distance for a fully loaded L-10E at 16,500 pounds to be 2100 feet at sea level. Takeoff distance varies with gross weight squared. For the takeoff at Lae the plane weighted about 14,000 pounds. 14,000/16,500 = 0.848 which squared equals 0.719 times 2100 feet means the takeoff at Lae should have taken 1,512 feet. Adding 243 pounds of fuel, and doing the same calculation results in a takeoff distance of 1,565 feet, only 53 feet longer, not much to worry about.

gl
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Mona Kendrick

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Re: Airworthiness Certificate(s); fuel capacity
« Reply #25 on: November 30, 2011, 10:13:09 AM »




  I might have considered gassing up and leaving Fred behind.  MHO

   Or maybe she should have left behind all that heavy gold bullion.  ;)
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Mona Kendrick

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Re: Airworthiness Certificate(s); fuel capacity
« Reply #26 on: November 30, 2011, 10:28:54 AM »

For the takeoff at Lae the plane weighted about 14,000 pounds. 14,000/16,500 = 0.848 which squared equals 0.719 times 2100 feet means the takeoff at Lae should have taken 1,512 feet. Adding 243 pounds of fuel, and doing the same calculation results in a takeoff distance of 1,565 feet, only 53 feet longer, not much to worry about.

gl

    Is your point that she should have considered 3000 feet plenty enough runway since the plane theoretically should have been able to get wheels off the ground in 1565 feet?  And does that figure take into account the unpaved runway surface and an elevated density altitude (high humidity and mid-morning temperature in the 80's)?  Yes, she got the wheels off at some point short of 3000 feet -- the takeoff video http://tighar.org/Projects/Earhart/ameliavideo.html shows her rotating, lowering the nose, and accelerating in ground effect.  But remaining runway is still a concern until the plane can start climbing out of ground effect.  In this case, she wasn't able to climb until over the water.

LTM,
Mona
« Last Edit: November 30, 2011, 11:19:18 AM by Martin X. Moleski, SJ »
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Harry Howe, Jr.

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Re: Airworthiness Certificate(s); fuel capacity
« Reply #27 on: November 30, 2011, 12:39:28 PM »




  I might have considered gassing up and leaving Fred behind.  MHO

   Or maybe she should have left behind all that heavy gold bullion.  ;)

But then the large eel (snake) and its friends the squid, the octopi, and the sharks wouldn't have anything to guard! ;D
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Gary LaPook

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Re: Airworthiness Certificate(s); fuel capacity
« Reply #28 on: November 30, 2011, 04:54:37 PM »

For the takeoff at Lae the plane weighted about 14,000 pounds. 14,000/16,500 = 0.848 which squared equals 0.719 times 2100 feet means the takeoff at Lae should have taken 1,512 feet. Adding 243 pounds of fuel, and doing the same calculation results in a takeoff distance of 1,565 feet, only 53 feet longer, not much to worry about.

gl

    Is your point that she should have considered 3000 feet plenty enough runway since the plane theoretically should have been able to get wheels off the ground in 1565 feet?  And does that figure take into account the unpaved runway surface and an elevated density altitude (high humidity and mid-morning temperature in the 80's)? 
LTM,
Mona
That estimate did account for the unpaved runway but did not account for the density altitude. I used the wrong weight, 14,000 pounds, her weight at Oakland. Her actual weight at Lae was probably only about 500 pounds more than at Oakland, she had about 150 gallons more fuel, weighing 900 pounds, but she was also short two people, Manning and Mantz, and their baggage, totaling about 400 pounds. So the weight was probably about 14,500 pounds but I will be conservative and overestimate the weight and use 15,000 for this calculation.

I have attached three years of data for 14 weather reporting stations in Papua New Guinea. This should be a representative sample and should validly predict the temperatures for 1937. Similar data would have been used in making the decision on whether  more power was needed for the takeoff at Lae. The nearest reporting station to Lae is Nadzab located 22 SM inland from Lae. The highest July temperature recorded there during the three year period was 30.1 ° C (86 ° F. ) The temperature should be lower at Lae since it is located on the coast. A 30 ° C temperature at a sea level airport produces a density altitude of 2,000 feet which would increase the takeoff distance by only 6% from the sea level density takeoff performance. Lockheed report 487 states that a sea level takeoff takes 2,100 feet so increasing this by 6% would predict a takeoff at a 2,000 foot density altitude would take 2,226 feet, well short of the 3,000 feet available at Lae. But even this distance is based on a gross weight of 16,500 pounds and we know the plane actually weighed no more than 15,000 pounds at Lae. Takeoff performance varies with the weight ratio squared. Dividing 15,000 by 16,500 gives 0.909 which squared makes 0.826 which multiplied by 2,226 feet gives the predicted takeoff run at Lae at a gross weight of 15,000 pounds and at a two thousand foot density altitude of 1,840 feet giving a safety margin for takeoff at Lae of more than 1,160 feet, a 63% safety margin.

The runway was grass at Lae and not paved. Modern takeoff performance data is calculated for paved runways but Lockheed did the calculation for a turf runway since paved runways were a rarity in 1937. Page 2 of report 487 states that it takes 2,100 feet to take off "on a hard run-way" so I can see why you would think the calculation was for a paved runway. But look at page 21, where they go through the actual calculation, where is shows that the calculation was for "a good field with hard turf." The calculation uses a coefficient of friction ( μ, mu) of .04 for the calculation which is the μ for turf. The μ  for pavement is .02, for short grass μ is .05 and it is .10 for tall grass. The coefficient of friction affects the takeoff roll because it retards the acceleration, the greater the μ the slower the acceleration. This retarding force gradually drops to zero as more and more of the weight of the plane is carried by the wings as speed increases. At the same time the drag due to increasing air resistance increases which slows down the acceleration as the plane approaches takeoff speed. All of these factors are accounted for on pages 21-23 which steps you through the calculation and you can redo the calculations yourself  by substituting your chosen value for μ. If you don't want to go through the entire calculation you can use a rule of thumb to come up with a reasonable adjustment for longer grass at Lae. The rule of thumb is to increase the distance for takeoff from a paved runway ( μ = .02) by 7% for turf, 10% for short grass and 25% for tall grass. First back out the 7% for the turf runway that the calculation assumed and then apply the percent increase for different runway surfaces.  But the runway at Lae was also described as "turf" and it looks like "turf" on the video, so the value calculated in report 487 should be applicable.  At the worst, the runway is "short grass" and not "tall grass." Using the rule of thumb would increase the takeoff distance only 50 feet more for "short grass" rather than "turf."

If you want, you can also use these formulas for calculating the takeoff distance for different gross weights and for density altitude. If adjusting for gross weight you must first calculate the takeoff speed using the normal formula for lift. The takeoff speed also determines the dynamic pressure, "q", which you need for the takeoff formula and also is needed for determining the final thrust from the table on page 21.

If you want to do the calculation for a different density altitude then you again calculate the takeoff speed but you must substitute the density of the air at the altitude that interests you. ρ at sea level conditions is .002378 slugs per cubic foot but gets less at higher density altitudes. You also use the air density in the takeoff formula as the divisor under the gross weight. In this case it is used in the form of pounds per cubic foot. You can calculate this value by multiplying ρ by 32.17 pounds per slug conversion factor. The other number that shows up in the formula, "458" is the wing area and is a constant.

I don't know if you fly supercharged airplanes but density altitude is not the bugbear for takeoff of supercharged airplanes that it is for naturally aspirated airplanes. This is because there are two ways density altitude (another way of describing the density of the air, rho, that changes with actual height above sea level and with temperature) affects takeoff performance. The first effect is that the airplane must accelerate to a higher true airspeed in order for the indicated airspeed (and q, the dynamic pressure) to increase to the level that the wings can make enough lift for the plane to get off the ground. If the Electra at standard sea level conditions took off at 85 mph indicated airspeed which is also 85 mph true airspeed at zero density altitude, it would still takeoff at 85 mph indicated airspeed but the true airspeed at 2,000 foot density altitude would be 87 mph. It takes a bit longer to accelerate to 87 than it does to 85.This effect on takeoff is equal to the inverse of the density ratio. Air at standard sea level conditions, zero altitude and 59° F, has a density of .002378 slugs per cubic foot while air at standard temperature at 2,000 feet (a 2,000 foot density altitude) has a density of .002242 making the density ratio of .9428. One divided by .9428 equals 1.06 so the takeoff should take about 6% more runway than at a density altitude of sea level.

The second effect that the air density has on takeoff performance is that the power output of the engine also drops off as the air gets thinner so the engines produce less thrust which then reduces the rate of acceleration so it takes even longer for the plane to reach the higher true airspeed needed to takeoff at a density altitude above sea level. This is a problem for airplanes with naturally aspirated engines but is NOT a problem with supercharged engines below the critical altitude since these engines produce full sea level power up to the critical altitude. The type certificate data sheet for the S3H1 engine shows  that the critical altitude for takeoff power of 600 horsepower is a 3,000 foot density altitude. This means that her S3H1 engines would produce full 600 hp takeoff power for the takeoff at Lae even if the temperature was 110 ° F but we know that it was no more than 86° F. The engines will also produce the 550 hp continuous rating up to a density altitude of 5,000.

Since these two effects parlay for an airplane with naturally aspirated engines, such a plane would use about 36% more runway at a 2,000 foot density altitude compared to zero density altitude. But since the Electra had supercharged engines and the density altitude did not exceed the critical altitude, the increase to the takeoff distance would be only the 6% previously mentioned.

And looking at the runway gradient, Long states that they had to taxi uphill to get to their starting position on the runway which would mean that they had a downhill gradient for takeoff which would help them and shorten the takeoff roll.

gl
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Mona Kendrick

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Re: Airworthiness Certificate(s); fuel capacity
« Reply #29 on: November 30, 2011, 06:29:59 PM »

Gary,
I'm still not clear what your point is.  The historical reality was that the plane used the full runway as reported by witnesses; you calculate that it should have or would have or could have needed less.  So . . . . ?

LTM,
Mona
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