Acheiving Best Economy Speed

Sam D

Sam D

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Sam D
Ok, at the risk of having my new complex endorsement taken away, I offer the following:

I have heard Mike Busch state that the speed for best economy works out to about 1.316 of your most aerodynamic speed (best glide is a good proxy for this).

So, assuming you'd be flying WOT, is it a matter of climbing to the appropriate altitude which gives you this speed?

Thanks,
Sam
 
However you determine it, don't forget to factor in the winds aloft. This is assuming you are going for maximum range, not maximum time aloft. -Skip
 
Contrary to what a lot of AFMs imply, your range at the altitude at which WOT gives you the appropriate speed will be the same as 100 AGL at the same IAS. Wind, as Skip pointed out, and minimum authorized altitudes (for IFR, obstruction clearance, etc.) is what determines the best altitude to use. But yes, that would be an appropriate method if that's the altitude you desire.

Prof Byington at ERAU has some good discussions online on the subject...http://www.db.erau.edu/research/cruise/

Fly safe!

David
 
By "best economy" do you mean lowest gph, or the "sweet spot' where gph and speed meet?

Lowest gph means a very low power setting, which means MCA if you want to maintain level flight. Generally a lot lower than Vbg, not higher. 'Nuff said about that.

The other kind of economy, where you're looking for the perfect blend of fuel economy and range, not merely endurance, depends, I think, on altitude, to some extent.

Flying at higher altitudes (up to a point) can give you a really good endurance-to-range margin, sometimes even with a lower IAS than, say, 1000 feet lower at the same power setting. It's a small target, for sure, at least wit the airplanes I'm familiar with... but I do know that the typical carbuereted 172 will get better range at, say, 70% power at 7500 feet than at 5500 feet. You sacrifice only a little airspeed for a significant fuel savings.
Go much higher, though, and you start to lose that margin, even though you can see higher airspeeds (up to a point). In such conditions, your range will suffer even though you're covering ground faster- you won't cover enough ground before you run out of fuel, compared to going a little slower but burning slightly fewer gph. It's like how the best flat-out airspeed will be seen near sea level, but fuel consumption will spike.

I'll have to look at a POH later to back this up, but that's how I remember it...
 
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Ron Levy said:
Your "best economy" speed is another name for "max range" (since you get the most range when you use the least fuel on the trip). For the absolute best words on that, see Prof. Mel Byington's paper on the subject at http://www.db.erau.edu/research/cruise/.
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Uh, thanks....
I read the first 2 pages, then moused through the rest of the article trying to find something to understand.
 
Another idea is to check out your airplane's POH. Remarkably, people spent a lot of time working out the numbers in there, which are generally fairly accurate, as to your speed and fuel burn. What you're really looking for is the airplane equivalent of miles per gallon, which you can do just with your TAS divided by GPH. The POH generally gives you the other effective means of determining your speeds of greatest efficiency by giving you what the plane's range is.

The Mooney, for example, will actually fly at about the same TAS at 12,000 as 5,000. The difference is it burns a lot less fuel doing it at 12,000. But, if at 12,000 I'm getting some monster headwind, I am probably better off at a lower altitude where I have less headwind anyway.

Really, I'd say just check the POH to give you some good guidelines, verify for yourself, and be happy. :)
 
Peggy,

Just remember, the only time you add power is when the headwind is MORE than 25% of the TAS, and then you only add power for 1 mph for each 2 mph OVER the 25% headwind.

Otherwise, best economy or Vz is WAY down there, about at 40% power. You can accomplish 95% of this at 55% power.
 
rottydaddy said:
Lowest gph means a very low power setting, which means MCA if you want to maintain level flight. Generally a lot lower than Vbg, not higher. 'Nuff said about that.
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Minimum controllable airspeed will involve slow flight, which involves a power increase after slowing through best range.

To find best range, decrease the RPM (for fixed pitch) by 100 and trim to achieve level flight. Note the new airspeed. Reduce it another 100 RPM, trim, and note again. Keep this up until the airspeed suffers a much larger drop than with the previous adjustments, and go back to the last setting before the big drop. There's your best range. Lean the engine aggressively, adjusting throttle to maintain the RPM.
Best endurance (time) is found by progressively reducing the power and trimming until the airplane won't hold altitude without adding power. The lowest power setting that will maintain level flight gives the longest time before landing. Used when the weather has trapped you and it might take a little time to clear so you can proceed, or if you're lost and need time to find yourself. Or if someone has clogged the runway with a wreck, maybe.

Dan
 
There's a lot of valid science out there. The article Ron linked to is excellent if you really want to figure this out from a rather academic point of view.

For a NA plane, it's pretty easy. Always fly WOT. Unless there is a strong head wind higher up, you'll always waste fuel otherwise. Control MP with altitude, not throttle.

For TC planes, the same applies. Choose the MP you're comfortable with and fly at the highest altitude where you can maintain it. For practical purpose, you might want to be lower. Best plan then is to control power with mixture. If you can't, reducing throttle will work, too, although you will obviously waste fuel.
 
MauleSkinner said:
Contrary to what a lot of AFMs imply, your range at the altitude at which WOT gives you the appropriate speed will be the same as 100 AGL at the same IAS. Wind, as Skip pointed out, and minimum authorized altitudes (for IFR, obstruction clearance, etc.) is what determines the best altitude to use. But yes, that would be an appropriate method if that's the altitude you desire.

Prof Byington at ERAU has some good discussions online on the subject...http://www.db.erau.edu/research/cruise/

Fly safe!

David
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sba55 said:
There's a lot of valid science out there. The article Ron linked to is excellent if you really want to figure this out from a rather academic point of view.

For a NA plane, it's pretty easy. Always fly WOT. Unless there is a strong head wind higher up, you'll always waste fuel otherwise. Control MP with altitude, not throttle.

For TC planes, the same applies. Choose the MP you're comfortable with and fly at the highest altitude where you can maintain it. For practical purpose, you might want to be lower. Best plan then is to control power with mixture. If you can't, reducing throttle will work, too, although you will obviously waste fuel.
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What's WOT?
 
sba55 said:
There's a lot of valid science out there. The article Ron linked to is excellent if you really want to figure this out from a rather academic point of view.

For a NA plane, it's pretty easy. Always fly WOT. Unless there is a strong head wind higher up, you'll always waste fuel otherwise. Control MP with altitude, not throttle.
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Of course, if you read the article, you'll find that these two statements contradict each other ;)

Fly safe!

David
 
sba55 said:
Which two arguments? Care to explain?

-Felix
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The article Ron posted says max range (best economy) is based on an angle of attack. You say it's based on throttle position. I don't believe that throttle position controls angle of attack.
 
MauleSkinner said:
The article Ron posted says max range (best economy) is based on an angle of attack. You say it's based on throttle position. I don't believe that throttle position controls angle of attack.
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No, I didn't say it was based on throttle position. In fact, if you read my comment, you'll notice that it assumes WOT throughout ;)

Also, keep in mind that I'm specifically not talking about max range. There are solutions to that - I don't completely understand them, nor do they matter to me because I can fly around at 170 TAS for nearly 6 hours.

From a practical point of view (as in, I have an airplane and I want to get somewhere), WOT is the way to go. Since you won't want to fly WOT at sea level, it's really a question of where you'll get a good speed/FF combination.

I imagine most pilots fly their planes at a power setting that gives them the speed they want and the engine longevity they need. Given that power setting, you'll get better speed and MPG at the max altitude for that setting.

-Felix
 
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There are two factors here that people are looking at, and each one contributes.

Felix is focusing on the engine perspective. On standard spark ignition engines (i.e. engines that have a throttle butterfly to control airflow), you'll experience a loss of efficiency as soon as you start to close that butterfly, because now the engine is having to pull a vacuum on the intake side of the engine. That takes horsepower, which in turn takes fuel. Compression ignition engines (or really engines that don't have a throttle body, which generally refers to diesel engines) have improved efficiency in part because they don't havve this restriction. Some turbo diesels actually manage to have higher intake pressure than exhaust pressure by properly sizing the turbo, and as a result gain increased efficiency still. So, Felix is focusing on the engine management side of things, which is definitely needed to get that best economy.

The airframe side of things has to do with angle of attack and drag. The higher your angle of attack, the more induced drag you have because the wing produces lift perpendicular to its chord line, so if you have a higher angle of attack, the plane actually starts producing lift in the opposite direction that you are trying to fly. No good. Additionally, you have basic aerodynamic drag, which just has to do with trying to push your airplane through the air, and the air not wanting to move to let the airplane through. Stupid physics.

Range is going to be your indication of your best economy. You have same amount of fuel potentially available (fuel level is X regardless of what speed you intend to fly), so the further you go with that amount of fuel, the more efficient you've been.

Once again, I'd suggest people have a look at the POH for a practical application of this info. If you want to learn the theory behind it, even better, but in terms of how it applies to you and your airplane, give that little thing a look. Yes, it is made with particular assumptions (specifically about engine operation), but if you choose an engine operating mode that makes it more efficient, even better. It'll still give you a good idea of where to start.
 
sba55 said:
I imagine most pilots fly their planes at a power setting that gives them the speed they want and the engine longevity they need. Given that power setting, you'll get better speed and MPG at the max altitude for that setting.
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I'd say that seems pretty accurate. The interesting thing, though, is that you can sometimes use a lower power setting (and thus lower fuel flow) at a higher altitude and still get the same airspeed. The Mooney is that way, for instance. I haven't yet made trips with it long enough to warrant getting up to some of those higher altitudes where the thing really gets efficient (>10,000 ft), but when I do, you better believe I'll get up that high, unless the winds are such that I'd be killing my speed, and thus not benefitting.
 
Dan Thomas said:
To find best range, decrease the RPM (for fixed pitch) by 100 and trim to achieve level flight. Note the new airspeed. Reduce it another 100 RPM, trim, and note again. Keep this up until the airspeed suffers a much larger drop than with the previous adjustments, and go back to the last setting before the big drop. There's your best range. Lean the engine aggressively, adjusting throttle to maintain the RPM.
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Ted DuPuis said:
Range is going to be your indication of your best economy. You have same amount of fuel potentially available (fuel level is X regardless of what speed you intend to fly), so the further you go with that amount of fuel, the more efficient you've been.

Once again, I'd suggest people have a look at the POH for a practical application of this info. If you want to learn the theory behind it, even better, but in terms of how it applies to you and your airplane, give that little thing a look. Yes, it is made with particular assumptions (specifically about engine operation), but if you choose an engine operating mode that makes it more efficient, even better. It'll still give you a good idea of where to start.
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I'd like to figure this out, Ted and Dan, because we fly long distances so often and soon we'll be living on retirement income. But our POH doesn't take into account that we have a 180 hp engine instead of 160, nor the STOL kit that made changes to our wings. And I've recently been informed we have a climb propeller instead of a cruise propeller.

and what's NA, TC, MP?
 
NA= Normally Aspirated
TC= TurboCharged
MP= Manifold Pressure (which for constant speed propellers is the measure of engine power, since RPM will not vary with throttle).
 
NA = Naturally Aspirated (what you have)
TC = Turbocharged (not what you have)
MP = Manifold Pressure (which you have no indication of on your fixed pitch prop plane)

Peggy, in your case since your POH doesn't have the info, I would start with looking at numbers from a POH of a later 172 with a 180 hp engine from the factory, and that would certainly be a good place to start. If you don't have any available, I may be able to find some for you. Even with the STOL changes to your wings, I would suspect that the plane would perform very similar to a later 180 hp 172.
 
Arnold_O said:
There is an article in the August edition of the AOPA website that uses Vy (best rate of climb) multiplied by 1.31 to get the most economical speed that your plane might travel at http://www.aopa.org/aircraft/articles/2008/080825asi.html

The article made sense and might be of great use to everyone for economical flight planning.
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Unfortunately, that number is valid only for the particular aircraft the author tested. That ratio is not based on any aerodynamic formulae or theory, just that pilots experiments with that aircraft type. If you want the best range IAS for your plane, you'll have to go through Byington's methodology.

Late addition: If you applied that method to a Grumman Tiger, it would tell you to use 118 KIAS at sea level and 105 KIAS at 10,000 feet. In fact, the correct number for the Tiger per Byington's methods (confirmed by my nearly 2000 hours in AA-5x's) is about 85 KIAS (very close to Vy), plus or minus depending on altitude.
 
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Ron Levy said:
Unfortunately, that number is valid only for the particular aircraft the author tested. That ratio is not based on any aerodynamic formulae or theory, just that pilots experiments with that aircraft type. If you want the best range IAS for your plane, you'll have to go through Byington's methodology.
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Bottom line, figure out the CAS for min power, divide by .76, and convert to IAS for max range.

Or, take the CAS for max range (determined above prior to IAS conversion), multiply by 1.07, and convert to IAS for Long Range Cruise IAS.

Takes about half an hour in the airplane, and another 20 minutes with the charts and a calculator ;)

Fly safe!

David
 
AuntPeggy said:
I'd like to figure this out, Ted and Dan, because we fly long distances so often and soon we'll be living on retirement income. But our POH doesn't take into account that we have a 180 hp engine instead of 160, nor the STOL kit that made changes to our wings. And I've recently been informed we have a climb propeller instead of a cruise propeller.

and what's NA, TC, MP?
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For around $500.00 you can get a fuel totalizer and couple it to a gps and it will give you mpg. If you really want to get there for the least amount of fuel it is far more accurate than using number crunching.

By the way my Viking gets the most mpg at 7500 than anything higher. I can go faster but I will loose some mpg doing it.

Dan
 
stingray said:
For around $500.00 you can get a fuel totalizer and couple it to a gps and it will give you mpg. If you really want to get there for the least amount of fuel it is far more accurate than using number crunching.

By the way my Viking gets the most mpg at 7500 than anything higher. I can go faster but I will loose some mpg doing it.

Dan
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I find that the NMPG feature of my JPI is not very useful. Wind, density altitude, etc. make a huge difference, so I've seen anywhere from 7 to 24 NMPG at the same mixture setting and altitude. Still interesting, though!
 
sba55 said:
I find that the NMPG feature of my JPI is not very useful. Wind, density altitude, etc. make a huge difference, so I've seen anywhere from 7 to 24 NMPG at the same mixture setting and altitude. Still interesting, though!
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That may be so, but unless there's an error in your fuel totalizer, it will tell you the nmpg you are getting on a specific flight and can be used to optimize the fuel efficiency on that flight.

BTW it is true that the power required for no wind max range airspeed is completely independent of altitude. Unfortunately the fuel efficiency of the engine can vary with altitude. Of course it varies with other things as well such as mixture, RPM, and power output. As a result it's likely that the airplane's no wind max range fuel efficiency would vary slightly with altitude, but since wind virtually always varies with altitude and wind has a greater effect on fuel efficiency than almost anything else besides speed, I suspect that any variation in engine efficiency with altitude will normally be swamped by the effects of wind.

BTW, fuel efficiency isn't the only component of flight cost. There are several costs besides fuel that are approximately proportional to flight time such as oil change cost, engine overhaul, engine accessory replacement/overhaul, gyro overhaul etc. When you consider these items the most cost effective airspeed may be well above max range speed. And that's ignoring the cost of your time, something that's even harder to pin down.
 
sba55 said:
I find that the NMPG feature of my JPI is not very useful. Wind, density altitude, etc. make a huge difference, so I've seen anywhere from 7 to 24 NMPG at the same mixture setting and altitude. Still interesting, though!
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How is that not useful if you are traveling. If you don't like what you see on the screen go higher (or lower) and if it gets worse try again. It may not do anything for specs but it will tell you where you get the best economy for the trip you are taking.

Dan
 
stingray said:
How is that not useful if you are traveling. If you don't like what you see on the screen go higher (or lower) and if it gets worse try again. It may not do anything for specs but it will tell you where you get the best economy for the trip you are taking.
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Don't get me wrong, I'm not saying that it's not useful. I just haven't found a use for it on my typical flights.

lancefisher said:
[...]BTW it is true that the power required for no wind max range airspeed is completely independent of altitude.[...]
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Lance, I don't doubt it. As I admitted before, I don't understand this, and for day to day operations, it hasn't been of any relevance. Nevertheless, maybe someone can explain it to me some day.....

-Felix
 
lancefisher said:
BTW, fuel efficiency isn't the only component of flight cost. There are several costs besides fuel that are approximately proportional to flight time such as oil change cost, engine overhaul, engine accessory replacement/overhaul, gyro overhaul etc. When you consider these items the most cost effective airspeed may be well above max range speed. And that's ignoring the cost of your time, something that's even harder to pin down.
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One of the guys here at work (not a pilot himself, but a 40-45 year veteran of this industry) put it to me simply: "People buy airplanes to get places fast." While a lot of us have other intentions when we go fly, there's definitely something to that.

A lot of it depends on whose rules you're operating under, though. If you're operating under your own rules, then you may be able to say that you're not going to change your engine at 2000 hours, you're going to change it when you have a reason to believe its life is ending. Theoretically, operating it at this lower power setting will decrease wear on it, so it should last longer (speaking in theory only, here).

But you're absolutely right, Lance, there's more to it than just the fuel cost, and that's easy to forget.
 
lancefisher said:
(snip)
BTW, fuel efficiency isn't the only component of flight cost. There are several costs besides fuel that are approximately proportional to flight time such as oil change cost, engine overhaul, engine accessory replacement/overhaul, gyro overhaul etc. When you consider these items the most cost effective airspeed may be well above max range speed. And that's ignoring the cost of your time, something that's even harder to pin down.
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True, if I can stretch my flight legs from current 350 nm to 380 nm, then a 1100 nm trip from NY to Oklahoma requires 1 less fuel stop, thus saving me the 30 to 60 minutes the third fuel stop requires.:yinyang: I can add the extra time into the total in my logbook and possibly reduce my insurance cost.
 
Ted DuPuis said:
One of the guys here at work (not a pilot himself, but a 40-45 year veteran of this industry) put it to me simply: "People buy airplanes to get places fast." While a lot of us have other intentions when we go fly, there's definitely something to that.
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This is pretty much where the common tendency to operate at around 65% power comes from. While this is a gross simplification of a complex issue, at 65% power most piston powered airplanes deliver a reasonable balance between "economy" and speed.

A lot of it depends on whose rules you're operating under, though. If you're operating under your own rules, then you may be able to say that you're not going to change your engine at 2000 hours, you're going to change it when you have a reason to believe its life is ending. Theoretically, operating it at this lower power setting will decrease wear on it, so it should last longer (speaking in theory only, here).
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Sure, if you have to comply with manufacturer's TBO limits (or the common part 135 TBO extensions), then an engine hour is an engine hour regardless of the power being developed. But even if you operate engines on an IRAN basis, I would expect that there's very little difference in average engine life in hours over the power settings we might use. I suppose you could make a case for engine life being more accurately represented by engine revolutions (i.e. RPM * time) and if that were true you'd want to consider revolutions per mile in the total cost equation. Then again it wouldn't surprise me to learn as some folks claim that most of the engine wear occurs during idle periods and startups. If that were true then there would be no difference in engine cost per mile at all when changing power and speed, but I find that a bit difficult to believe.
 
Also, Peggy, I don't believe you all are doing any operations which require you to adhere to any replacement schedules. As such, if your engine has more hours on it but is still in good condition, the only thing preventing you from continuing to run it is your comfort level.
 
sba55 said:
Don't get me wrong, I'm not saying that it's not useful. I just haven't found a use for it on my typical flights.
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I have occasionally used nmpg (or it's cousin, fuel remaining after landing) to influence my power settings. The most common situation is when unforecast winds are eating into my planned fuel reserve and in that case I will change altitude and/or slow down until the desired reserve is restored.


Lance, I don't doubt it. As I admitted before, I don't understand this, and for day to day operations, it hasn't been of any relevance. Nevertheless, maybe someone can explain it to me some day.....

-Felix
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The reason the issue of altitude vs max range seems so counterintuitive is because we rarely fly anywhere near as slow as max range speed unless we are flying very high where the available power limits indicated speed to something close to max range.
 
Ted DuPuis said:
Also, Peggy, I don't believe you all are doing any operations which require you to adhere to any replacement schedules. As such, if your engine has more hours on it but is still in good condition, the only thing preventing you from continuing to run it is your comfort level.
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Right. The only passengers are kids, grandkids, and the occasional friend, possibly hitchhiker.
 
One thing that's missing from all of this discussion...

Everyone's talking about level flight. Sure, flying at the best range power setting at the altitude where you can do so WOT is theoretically best, but let's say that's 12,000 feet and I'm only going 40nm away. How much of that efficiency is lost by having to climb so far? Also, what is the best possible compromise for a cruise climb, or is it really best to climb Vy to your final altitude?

I've been wondering about these things for a while...
 
Ok, I'm prolly the cheapest SOB you'll ever find with an airplane. I can squeeze two Nickels and make a dime in change so here's my profile for distance trips(not pattern stuff). I have a Bonanza, but the rules apply for any complex plane.

First rule. Lean all the time. I don't care what phase of flight, pull the mixture. The ONLY time you run full rich is on take off. If you have an multi-EGT, you may start leaning in climb to your target takeoff EGT reading, or slightly lower EGT.

Next, turn down the fan speed. Several reasons for this. One is that the most efficient Otto cycle(4 stroke) engine speed is that which optimizes incoming air charge, and cam timing. With the throttle wide open, you're getting all the air you can. Manage power settings with the prop. I regularly run as low as 1850RPM. Another bonus, you won't believe how quiet a plane can be at low engine speed. Also, the prop is generally more efficient at slower speed.

Fly any altitude you like. Just remember, you're only slightly more efficient at altitude, but you are faster. Pick the altitude that gives the best winds aloft assist, or least detriment. I've flown 600 miles at only 1200AGL cause the wind was favorable. The bugs are a problem, but they'll clean off.

Pick a speed that is about 20MPH over the best glide for your plane. This is a rule of thumb that comes from those graphs showing best economy speeds. The Bonanza best glide is 122-132MPH based on weight. If I'm at gross my selection is about 155MPH. This gives me a modestly faster speed with only a small increase in fuel flow. I could go 132MPH but there are other reasons not to with the engine running, primarily because the thermodynamic efficiency is less at that speed.

Learn to glide and soar. This is more important in the mountains than the flats. If you're in rising air, slow down by pulling the prop back, or by simply pulling up on the yoke. Gliding, I never touch the mixture until I'm just about in the pattern, or maneuvering for landing. If I'm cruising at 11,500' and landing at 800', I can turn the power back a good 400RPM and glide at 400FPM which keeps the same speed, but uses a lot less fuel. When I go to CO, I always find ridge lift, once I had to pull the engine back to idle and was still going up at +500FPM.

Fill your tank when it's cool. A lot of people don't know that fuel changes density with temp. It's true, you get more fuel per gallon at lower temps. Also, try to fill when the plane is cool too. Since it's a distance trip, you're prolly leaving with full tanks. Some planes have huge fuel reserves. It doesn't pay to carry 100 gallons around if you're only going 400 miles R/T. I like to fuel just before I leave, and I like to leave in the morning so this works out well. Better than fueling when you get back.

Clean your plane, and most important dress your prop. The prop is prolly the one place where a pilot can make the most difference. I keep mine spotless as possible. I'm ready to strip and paint it again because of the small paint chips. 80% of the thrust is made at the out 20% of the blade. That part of the prop is super important.

Finally, fly straight lines. Go through MOAs(shared use), go through R space with authorization, go through Class B when needed, go through anything you want to maintain a straight line. I have the cheapest GPS known to humans, but one thing it'll do just fine is draw a straight line on the display.
 
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flyingcheesehead said:
One thing that's missing from all of this discussion...
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I'll answer some of them based on my own experience....

flyingcheesehead said:
Everyone's talking about level flight. Sure, flying at the best range power setting at the altitude where you can do so WOT is theoretically best, but let's say that's 12,000 feet and I'm only going 40nm away. How much of that efficiency is lost by having to climb so far?
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40NM/12,000' is excessive, but you generally regain fuel you used in the climb in the descent. It's pretty close to a zero sum game.

flyingcheesehead said:
Also, what is the best possible compromise for a cruise climb, or is it really best to climb Vy to your final altitude?

I've been wondering about these things for a while...
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That really depends on a lot of factors.

On my plane, for example, Vy is 96. I've found, however, that there's virtually no difference in climb performance between 96 and 120 KIAS. It makes a huge difference in CHTs, however, and I therefore never ever climb at 96.

I think keeping CHTs low in the climb is a lot more important than saving a few gallons. Additionally, leaning is going to make a much bigger difference in the climb. There's no reason not to lean as soon as you take off (forget the whole deal about not leaning below 5000 or whatever feet, it's wrong). I generally lean as soon as I notice that EGTs have fallen a bit below what they were a few moments after takeoff when I normalized the EGT display.

As for pulling the prop back - I like to do that, too, but only at the appropriate power settings. My max RPM is 2700, and while I will reduce to 2550 for noise abatement, I won't go any lower until I can be sure that ICPs are low enough, especially ROP. Lower RPM = higher ICPs. High ICP & CHT are the main engine killer.

-Felix
 
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docmirror said:
Pick a speed that is about 20MPH over the best glide for your plane. This is a rule of thumb that comes from those graphs showing best economy speeds.
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Bad thumb. It may work well for aircraft with similar aerodynamics to your Bo, but it is not even close to correct across the board, especially for fixed gear aircraft. The only way to find the right speed is to get in the book for your plane and do the figuring like ol' Mel says.
 
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