Advanced search  
Pages: 1 2 3 [4]   Go Down

Author Topic: Fuel load, head winds, range  (Read 50276 times)

Martin X. Moleski, SJ

  • Administrator
  • *
  • Posts: 2960
Re: Fuel load, head winds, range
« Reply #45 on: December 21, 2011, 12:10:02 PM »

A third article has been published in the December 2011 European Journal of Navigation by the originator of this thread here.
LTM,

           Marty
           TIGHAR #2359A
 
Logged

Heath Smith

  • T4
  • ****
  • Posts: 391
Re: Fuel load, head winds, range
« Reply #46 on: December 21, 2011, 12:28:26 PM »


Wow, excellent article. Many thanks!
Logged

Bruce Thomas

  • Administrator
  • *
  • Posts: 647
  • Now where did I put my glasses?
Re: Fuel load, head winds, range
« Reply #47 on: December 21, 2011, 02:48:10 PM »

A third article has been published in the December 2011 European Journal of Navigation by the originator of this thread here.
Although I'm about 5 weeks late doing so, seeing Mr. van Asten's name reminds me to wish him a happy 80th birthday!
LTM,

Bruce
TIGHAR #3123R
 
Logged

Richard C Cooke

  • T1
  • *
  • Posts: 35
Re: Fuel load, head winds, range
« Reply #48 on: December 21, 2011, 02:59:23 PM »

My question for Richard is this, didn't Earhart need to stick to the flight plan and adjust her heading based on the magnetic declination that she experienced during the flight?

Isn't it critical to adjust your airspeed to match the 150 mph ground speed so that the magnetic influences of the Earth are kept in check when it comes to following your compass heading?

It seems that if you deviate from the plan, as you suggested using a 138 mph ground speed, this would throw a wrench in the entire flight plan? Perhaps I am missing something?

Thank you in advance.
Hi Heath

I don't know of any reason for AE to hold a fixed ground speed.

To get optimum range your need to fly faster in the beginning, when the plane is heavy, (L487 starts out with a speed of 162mph) and slower near the end of the flight, so its not a fixed speed.

We know that AE did not hold a 150mph ground speed because if she had she would have covered the 2556 miles in 17hours, as per the strip chart.  Then she would have made her "I must be on you" call 17hrs after take off, not after 19hr 12min.  The 133mph ground speed I gave is from a simple calculation of dividing 2556 by 19.2hrs to give an estimate of the actual ground speed.

Richard
Logged

Heath Smith

  • T4
  • ****
  • Posts: 391
Re: Fuel load, head winds, range
« Reply #49 on: December 21, 2011, 03:32:05 PM »


Richard,

Didnt the flight plan require exact time and magnetic compass measurements with a fixed ground speed?

Maybe her showing up late is evidence that this was not possible for them, that they could not determine ground speed?

Thanks.
Logged

Martin X. Moleski, SJ

  • Administrator
  • *
  • Posts: 2960
Re: Fuel load, head winds, range
« Reply #50 on: December 21, 2011, 06:13:25 PM »

A third article has been published in the December 2011 European Journal of Navigation by the originator of this thread here.
Although I'm about 5 weeks late doing so, seeing Mr. van Asten's name reminds me to wish him a happy 80th birthday!

Hear, hear!
LTM,

           Marty
           TIGHAR #2359A
 
Logged

John Ousterhout

  • T4
  • ****
  • Posts: 487
Re: Fuel load, head winds, range
« Reply #51 on: December 21, 2011, 07:13:34 PM »

Three things to keep in mind  - 1) best economy airspeed increases with weight,  2) best economy airspeed decreases with decreasing weight, and 3) "economy" gets worse with increasing weight.
In a heavy weight condition, the "best" economy airspeed still sucks gas at a prodigious rate, compared to fuel consumption when lightly loaded, but it gets you towards your destination.  As your weight decreases, you can slow down to a new, "better" most-economical airspeed.

Here's the heart of the conundrum - the most economical airspeed for the lightly loaded aircraft is too slow to even stay in the air for the heavy aircraft, so you're forced to fly faster, even though you're burning more fuel.  That's why the Lockheed engineer gave AE the information for airspeeds and power settings to obtain best range.  He gave the best "MPG" speeds as the fuel weight decreased during the flight in easy incremental steps.

An unexpected headwind would mean that the amount of fuel remaining after X hours is the same as if there were no wind.  The difference is that you might have further to fly after X hours to reach your destination.  The best speed and power setting for best fuel economy didn't change, and those things are determined by air miles, not ground miles.
Cheers,
JohnO
 
Logged

Ricker H Jones

  • TIGHAR member
  • *
  • Posts: 114
Re: Fuel load, head winds, range
« Reply #52 on: December 22, 2011, 11:27:15 AM »

I would like to convey this message from Mr. Van Asten:
" Bruce Thomas , on the TIGHAR site , wishes me a happy 80th birthday . Would you plse thank him inmy name since I canĀ“t do it myself , having no entrance to the site . Thank you very much in advance . H ."
Rick
Logged

Gary LaPook

  • T5
  • *****
  • Posts: 1624
Re: Fuel load, head winds, range
« Reply #53 on: December 23, 2011, 01:31:08 AM »

Three things to keep in mind  - 1) best economy airspeed increases with weight,  2) best economy airspeed decreases with decreasing weight, and 3) "economy" gets worse with increasing weight.
In a heavy weight condition, the "best" economy airspeed still sucks gas at a prodigious rate, compared to fuel consumption when lightly loaded, but it gets you towards your destination.  As your weight decreases, you can slow down to a new, "better" most-economical airspeed.

Here's the heart of the conundrum - the most economical airspeed for the lightly loaded aircraft is too slow to even stay in the air for the heavy aircraft, so you're forced to fly faster, even though you're burning more fuel.  That's why the Lockheed engineer gave AE the information for airspeeds and power settings to obtain best range.  He gave the best "MPG" speeds as the fuel weight decreased during the flight in easy incremental steps.

An unexpected headwind would mean that the amount of fuel remaining after X hours is the same as if there were no wind.  The difference is that you might have further to fly after X hours to reach your destination.  The best speed and power setting for best fuel economy didn't change, and those things are determined by air miles, not ground miles.
Well actually, a headwind requires a slight increase in airspeed to minimize the deleterious effect of the headwind. The rule of thumb is to increase the airspeed 1/4th of the headwind component and Lockheed report 487 shows this. But this is only true if you are already flying at the most efficient airspeed. For example, let's say that the best range airspeed is 100 knots. If you are flying at 100 knots into a 100 knot headwind then just maintaining the airspeed at 100 knots means that you are going nowhere so you should increase your airspeed to 125 knots. If you are flying faster than the most efficient airspeed then maintaining that airspeed may be the best policy. Continuing the example, say you had been flying at 130 knots instead of 100 knots into the 100 knot headwind. Just maintaining the 130 knots gets you very close to the new best range airspeed of 125 knots.

What we know of Earhart's method is that she never flew slow enough to be at the best range speed based on the weight. The fuel capacity of he plane was enough so that it was not necessary to do so. She averaged about 145 mph on the other legs of the flight and this would not have been possible if she had been flying at best range speeds that were well under this number at light weights. On the leg from Natal to St. Louis she averaged 149 mph for the 1971 SM leg. From the chart for the Dakar flight, and from the Williams strip charts, it is clear that they based their preliminary flight planning on a ground speed of 150 mph but there was no necessity to stick to that number if there was a surfeit of fuel available as it was on the other legs.

The 1912 Z report shows that the ground speed had been at least 133 mph and possibly even faster if Earhart didn't make this report at the exact instant that they thought they had arrived and, as is likely, they had not flown directly to Howland but had added some miles for performing the sun line landfall approach. Since all the information we have shows about a 25 knot (28 mph) headwind component, to achieve a ground speed of 133 mph would have required an airspeed of 161 mph, well above the best range speed as the plane got lighter.

gl

« Last Edit: December 25, 2011, 01:58:03 AM by Gary LaPook »
Logged

Heath Smith

  • T4
  • ****
  • Posts: 391
Re: Fuel load, head winds, range
« Reply #54 on: December 23, 2011, 07:46:40 PM »

Quote
The rule of thumb is to increase the airspeed 1/4th of the headwind component and Lockheed report 487 shows this.

Are you referring to the chart on page 10?

I am wondering if this was not trying to calculate the air speed needed to achieve a ground speed but rather it was given only to show the change in the GPH efficiency?
Logged

Gary LaPook

  • T5
  • *****
  • Posts: 1624
Re: Fuel load, head winds, range
« Reply #55 on: December 23, 2011, 08:34:08 PM »

Quote
The rule of thumb is to increase the airspeed 1/4th of the headwind component and Lockheed report 487 shows this.

Are you referring to the chart on page 10?

I am wondering if this was not trying to calculate the air speed needed to achieve a ground speed but rather it was given only to show the change in the GPH efficiency?
The graph on page 10 is the standard way for finding the best range airspeed, NOT ground speed. You plot fuel flow rate (or power required) on the X axis and airspeed on the y axis. You then draw a line from the origin tangent to the curve and read the best range airspeed from the point of tangency. Shifting the starting point of the line right or left is how you figure the best range airspeed depending on wind. This is all standard engineering.
gl
Logged

Jeff Scott

  • T2
  • **
  • Posts: 93
Re: Fuel load, head winds, range
« Reply #56 on: December 24, 2011, 05:22:04 PM »

A third article has been published in the December 2011 European Journal of Navigation by the originator of this thread here.

One of the puzzling aspects of Mr. van Asten's time with us was his very difficult to read writing style that made many of his points hard if not impossible to understand. Had he communicated with the same talent displayed in this article, he would have gotten along just fine!
It's not too late to be great.
 
Logged

Heath Smith

  • T4
  • ****
  • Posts: 391
Re: Fuel load, head winds, range
« Reply #57 on: December 24, 2011, 06:27:11 PM »

Quote
The 1912 Z report shows that the ground speed had been at least 133 mph and possibly even faster if Earhart didn't make this report at the exact instant that they thought they had arrived and, as is likely, they had not flown directly to Howland but had added some miles for performing the sun line landfall approach. Since all the information we have shows about a 25 knot (28 mph) headwind component, to achieve a ground speed of 133 mph would have required an airspeed of 161 mph, well above the best range speed as the plane got lighter.

Gary,

Have you ever created your own model of the entire flight from Lae to Howland and made an estimate of the fuel remaining? If so, can you post those results?

Thanks.
Logged

Gary LaPook

  • T5
  • *****
  • Posts: 1624
Re: Fuel load, head winds, range
« Reply #58 on: December 25, 2011, 03:46:17 AM »

A third article has been published in the December 2011 European Journal of Navigation by the originator of this thread here.

One of the puzzling aspects of Mr. van Asten's time with us was his very difficult to read writing style that made many of his points hard if not impossible to understand. Had he communicated with the same talent displayed in this article, he would have gotten along just fine!
I have read his third article and it is gibberish like the prior two. I am not going to get sucked into dissecting  every aspect of this article but I will point out four items.

1. He uses the wrong weight for the plane, 16,400 pounds, while the weight at takeoff did not exceed 15,000. What is interesting in that it demonstrates Mr. van Asten's lack of knowledge by the way he calculated this. He started with the maximum gross weight of 16,500 pounds and subtracts 1,200 gallons of fuel weighing 7,200 pound giving him an empty weight of 9,300 pounds. He then adds the 6,600 pounds for the 1,100 gallons of gas the plane carried on takeoff from Lae plus 500 pounds for the crew and equipment coming up with his 16,400 pounds. What is wrong with this is his assumption that the only payload of the plane was the 1,200 gallons of fuel, he left out the crew, equipment and any cargo from the beginning of his calculation. The documentation actually shows that the empty weight was 7,340 pounds not the 9,300 upon which van Asten based his calculations. To this real empty weight we add 340 pounds of crew, 6,600 pounds of fuel, 562 pounds of oil for a total of 14,842 pounds leaving some extra capacity for equipment before exceeding 15,000 pounds. The effect of weight on range is inversely proportional to the weight and van Asten overestimated the weight by 9 or 10% causing him to underestimate the range by the same 9 or 10%.

2. He calculated the time to fly from Lae to Howland as exactly 18 hours, 50 minutes and 8 seconds but he doesn't tell us where he started the timing from, was it at the beginning of the takeoff roll, or when the tail came up, or when the main wheels left the ground, or when they cleared the end of the runway, or some other blade of grass on the runway. Mr. van Asten uses impossible levels of precision in his calculations which mean nothing in the real world.

3. He uses the Breguat formula for part of his calculations but this formula is only valid if the plane is flown, at all times, at exactly its best range speed which get slower and slower as the plane burns off fuel and gets lighter and we know Earhart did not follow the Breguat regime but flew at considerably higher speeds, so the use of that formula is invalid for van Asten's calculations.

4. I get a real chuckle out of this one, he now admits the position report was received at Lae at 0718 Z when in his prior arguments he claimed it was sent at 0720 Z in support of his complex calculations that showed that Noonan took an observation of the sun at exactly 0719:30 Z to produce that position report but this claimed observation would have been taken one and a half minutes after the report had been received at Lae. Now that he admits that the report was received two minutes prior to the time that he thought the position report had been sent from the plane, this shows that he was wrong since you can't receive a radio report earlier than the time that it was sent. This was the subject of several months of postings earlier this year. A minute and a half error may not sound very significant to readers but it was absolutely critical to van Asten's theory in his two prior articles, everything flowed from that erroneous computation. In celestial navigation a one and a half minute difference in the time of a sight is HUGE since it produces an error of 29 SM because the plane is moving and, more significantly, the Earth is turning at a rate 1,035 mph - 17.25 SM per minute. (I wonder if he will now go back and retract his prior erroneous articles but I doubt that he will.)

Here are links to what I have written about the quality of van Asten's prior articles.
Link1, link2 link3.


So you can try to decipher his most recent article if you want. good luck.

gl
« Last Edit: December 28, 2011, 12:35:06 AM by Gary LaPook »
Logged

Jeff Scott

  • T2
  • **
  • Posts: 93
Re: Fuel load, head winds, range
« Reply #59 on: December 28, 2011, 07:04:57 PM »

A third article has been published in the December 2011 European Journal of Navigation by the originator of this thread here.

One of the puzzling aspects of Mr. van Asten's time with us was his very difficult to read writing style that made many of his points hard if not impossible to understand. Had he communicated with the same talent displayed in this article, he would have gotten along just fine!
I have read his third article and it is gibberish like the prior two. I am not going to get sucked into dissecting  every aspect of this article but I will point out four items.

My statement is certainly not an endorsement of his methods or conclusions, merely a comment on the writing style. His latest article still contains grammar issues that I assume are due to English not being his native language. I think we can all forgive this, although I find it odd that a professional journal wouldn't ensure a proper editing job was done.
It's not too late to be great.
 
Logged
Pages: 1 2 3 [4]   Go Up
 

Copyright 2019 by TIGHAR, a non-profit foundation. No portion of the TIGHAR Website may be reproduced by xerographic, photographic, digital or any other means for any purpose. No portion of the TIGHAR Website may be stored in a retrieval system, copied, transmitted or transferred in any form or by any means, whether electronic, mechanical, digital, photographic, magnetic or otherwise, for any purpose without the express, written permission of TIGHAR. All rights reserved.

Contact us at: info@tighar.org • Phone: 610-467-1937 • Membership formwebmaster@tighar.org

Powered by MySQL SMF 2.0.15 | SMF © 2017, Simple Machines Powered by PHP