Horsepower debate (was DA40NG)

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lsctommy

Horsepower debate (was DA40NG)

Post by lsctommy »

It's ALWAYS better to have more horse power and not need it than to have less horse power and need it.
You can alway pull back power, go slower and consume less if you so desire. You can't do the opposite if you're already full power and you wish you had more power. The same goes for cars, motorcycles, boats etc. All of the Diamond products are currently way underpowered. Of course, when you increase power you also increase weight via a bigger power plant and or more fuel. You can't fight physics. It is what it is.
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Re: DA40NG

Post by CFIDave »

lsctommy wrote:All of the Diamond products are currently way underpowered.
Really? If I can out climb a BE58 Baron in a DA42-VI, or "levitate" off the runway climbing in a DA40, or cruise nearly 200 knots TAS in my DA62, please explain how these planes are underpowered.

Diamond's slick, efficient, modern composite airframes with long high aspect-ratio wings require fewer horsepower for similar performance as GA aircraft originally designed in the 1950s-1970s -- with major savings in fuel consumption and no need for "wet wings" (that catch fire in accidents) to carry prodigious amounts of fuel.
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Re: DA40NG

Post by Don »

lsctommy wrote: All of the Diamond products are currently way underpowered.
One of the most ridiculous comments I have ever read on this forum. Yesterday, I had four adults in my DA40-XLS. We were climbing out at more than 1000 feet per minute. Just saying.
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Re: DA40NG

Post by Antoine »

lsctommy wrote:It's ALWAYS better to have more horse power (...). Of course, when you increase power you also increase weight via a bigger power plant and or more fuel. You can't fight physics. It is what it is.
What a strange comment from an unknown poster. You even manage to answer and demolish your own opening statement...

Diamond products underpowered?

Here a true story. A good friend of mine used to own a Cessna 182 with 240 HP.
I took her flying. She was immediately stunned by the 1'000 fpm initial climb of the DA40 XLS at gross.
And in cruise the '40 was outrunning her poor 182 despite sipping 3 USG less per hour.
240 vs 200 horsepower... which one would you rather fly?
In her case it was a no brainer. She sold the 182...

As I said many times, the DA40-180 is a perfectly balanced work of art.
Balance means that 200 horses, 9 GPH and 50 gallon tanks are just right. Add horsepower and you lose useful load and range. In over 1'000 hours I never felt DA40s were lacking power.
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Re: DA40NG

Post by Sandy »

Antoine wrote:And in cruise the '40 was outrunning her poor 182 despite sipping 3 USG less per hour.
240 vs 200 horsepower... which one would you rather fly?
Am I missing something? I thought that the IO-360 in my DA40 is rated at 180 Hp.

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Re: DA40NG

Post by Tommy »

lsctommy wrote:It's ALWAYS better to have more horse power and not need it than to have less horse power and need it.
You can alway pull back power, go slower and consume less if you so desire. You can't do the opposite if you're already full power and you wish you had more power. The same goes for cars, motorcycles, boats etc. All of the Diamond products are currently way underpowered. Of course, when you increase power you also increase weight via a bigger power plant and or more fuel. You can't fight physics. It is what it is.
This is my post. At the time and for whatever reason I couldn't post using my forum name.
CFIDave wrote:
lsctommy wrote:All of the Diamond products are currently way underpowered.
Really? If I can out climb a BE58 Baron in a DA42-VI, or "levitate" off the runway climbing in a DA40, or cruise nearly 200 knots TAS in my DA62, please explain how these planes are underpowered.

Diamond's slick, efficient, modern composite airframes with long high aspect-ratio wings require fewer horsepower for similar performance as GA aircraft originally designed in the 1950s-1970s -- with major savings in fuel consumption and no need for "wet wings" (that catch fire in accidents) to carry prodigious amounts of fuel.
Dave, you can't out climb a BE58. The book numbers just don't support your claim. In addition and just to note, your comparison is a turbocharged Austro vs. a normally aspirated Lycoming. Kind of apples and oranges comparison. If you were to compare a turbocharged Lycoming to the turbocharged Austro, there would be no comparison. 200kts. TAS, sorry Dave, the numbers again don't support the claim, especially if you operate at the recommended power setting. I didn't find levitation tables. Yes Dave, the Lycomings do suck up the fuel. That's why they blow the doors off the Austros. The more fuel you suck up, the more doors you blow off. Yes Dave, the fuel system design of the Diamonds is superior to just about anything out there. If I crash I will burn up. If you crash odds are you won't.
Antoine wrote:
lsctommy wrote:It's ALWAYS better to have more horse power (...). Of course, when you increase power you also increase weight via a bigger power plant and or more fuel. You can't fight physics. It is what it is.
Don wrote:
lsctommy wrote: All of the Diamond products are currently way underpowered.
One of the most ridiculous comments I have ever read on this forum. Yesterday, I had four adults in my DA40-XLS. We were climbing out at more than 1000 feet per minute. Just saying.
Well Don, it was an inaccurate statement. The "most ridiculous," no, just inaccurate. The Lycoming powered Diamonds are adequately powered in my opinion. When I made the statement I had my mind focused on diesels.
Antoine wrote:
lsctommy wrote:It's ALWAYS better to have more horse power (...). Of course, when you increase power you also increase weight via a bigger power plant and or more fuel. You can't fight physics. It is what it is.
What a strange comment from an unknown poster. You even manage to answer and demolish your own opening statement...

Diamond products underpowered?

I'm not quite sure what you are questioning Antoine, or maybe I just am not clear about what I was trying to convey. If you want more power it requires a bigger engine which requires more fuel which equals more weight which equals more performance. The performance gain far out weighs the weight gain.
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Re: DA40NG

Post by Antoine »

Sandy wrote:
Antoine wrote:And in cruise the '40 was outrunning her poor 182 despite sipping 3 USG less per hour.
240 vs 200 horsepower... which one would you rather fly?
Am I missing something? I thought that the IO-360 in my DA40 is rated at 180 Hp.

Sandy
Sandy it would have been unfair in this comparison to ignore the 23 extra HP from the powerflow tuned exhaust. They are real although Diamond were too lazy to update the POH so they left it at the "old performance numbers".

Tommy: sorry mate - I would have been more courteous if I had know it was you. :D
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Re: DA40NG

Post by CFIDave »

Tommy wrote:Dave, you can't out climb a BE58. The book numbers just don't support your claim. In addition and just to note, your comparison is a turbocharged Austro vs. a normally aspirated Lycoming. Kind of apples and oranges comparison. If you were to compare a turbocharged Lycoming to the turbocharged Austro, there would be no comparison. 200kts. TAS, sorry Dave, the numbers again don't support the claim, especially if you operate at the recommended power setting. I didn't find levitation tables. Yes Dave, the Lycomings do suck up the fuel. That's why they blow the doors off the Austros.
First, I actually did out-climb a BE58 Baron in my DA42-VI. We were conducting a formation photo shoot with my friend (another CFI) flying his 2001 BE58 Baron alongside in cruise. He had two people onboard (one was my pilot wife taking pictures) and I was alone in the DA42. We started out level at about 5000 feet when we both decided to climb at max rate. Quite frankly we were all surprised at the result, since it contradicts the "book numbers" that you cite that show the Baron's superior sea-level climb performance (which I don't dispute). And yes, Austros have turbos, the pair of 300 hp (at sea level only) Continentals on the Baron do not, but the turbo is what contributes to Diamond twin performance and can't be ignored in your "underpowered" opinion.

My "levitation" comment about the DA40: One of the really cool (and somewhat unusual) features I like to demonstrate flying DA40s (especially for people who've never flown a Diamond) is that you can often take off without having to rotate or pitch the nose up; the plane seems to almost "levitate" in a level attitude as if riding an elevator on takeoff -- due to the lift of Diamond's sailplane-derived airfoil and 40 foot wing. This is hardly what you might expect from an "underpowered" aircraft.

As for the TAS of my DA62, I guess I'll have to take a photo of my cruise airspeed next time. Book airspeeds are often measured by test pilots flying at maximum gross weight, which is rarely the way DA62s are flown given their generous useful load and minimal need to fly with full fuel. In addition, I know many Diamond Austro owners who normally fly at maximum continuous power (92% on DA40/42 NGs or -VI, 95% for the DA62) for hours in cruise with no ill effects on their engines; I do it when I need to get somewhere in a hurry or want to reduce exposure to strong headwinds.

Finally, by focusing exclusively on engine horsepower (and related fuel flows), you seem to ignore the greater performance effects of reduced aerodynamic drag and high-aspect ratio wings that permit Diamonds to perform as well with less horsepower vs. draggy old aluminum designs with shorter wings and bigger thirstier engines.
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Re: DA40NG

Post by Tommy »

Horse power is the single most dominant factor when one looks at performance, aerodynamics help, but it's not going to get you there in any big way. Again, base line poh performance numbers are what should be looked at when comparing aircraft, nothing else. As you know the Diamond 62 poh gives performance numbers at and well under gross weight.

Again Dave, you continue to cherry pick performance i.e starting at 5,000' or sea level. Your max speed is at only one altitude, I believe 16,000' msl while being slower at all others. How about looking at the whole spectrum like "time to climb to altitude" and then look at the performance at the different altitudes. How about looking at TAS at all altitudes and not focusing on the best TAS at only one altitude.

There must be a reason why the manufacturer in the poh states thats the recommended cruise setting is 75% and not 92%. If it's not necessary and poses no degradation or ill effects why is it there? Diesel's have their own set of problems, they are not a panacea. How about those ECUs and the wonderful gear boxes vs. direct drive. There isn't and airplane made out there diesel or avgas that has not had nothing but problems with gear boxes. It's just another component to fail that direct drive does not have.

Again Dave, you are right in that there are many fine attributes of all of the Diamond products that everyone gives a different weight to. Safety is the obvious one with little competition from others. Composites have their advantages and disadvantages as does aluminum. Some places only have diesel fuel. I get it. Let's just lay it all out there and not hide behind selected characteristics. You and I both want everyone on this forum to be well informed. An ill informed owner who finds things out after the fact is not a happy owner.

By the way, old aluminum airplanes are not going away any time soon. Not when you can totally refurbish an aircraft with zero time engines including new plumbing throughout, complete state of the art avionics, complete new interiors and a new paint scheme for less than half the cost of a comparable new airplane.
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Re: DA40NG

Post by CFIDave »

Tommy wrote:Horse power is the single most dominant factor when one looks at performance, aerodynamics help, but it's not going to get you there in any big way.
Nope. Let's talk about speed (technically velocity) as one aspect of performance. Looking at the math, the force required to overcome drag increases with the square of velocity, and horsepower needed to overcome drag increases with the cube of velocity. So adding more horsepower provides diminishing returns if you want to fly faster.

But another way to go faster is to reduce the drag force (either coefficient of drag and/or less frontal area) with a slicker airframe. Reducing drag has the same proportional effect as increasing horsepower. We could get into a similar discussion in discussing climb rates, looking at factors like excess horsepower, coefficients of lift, etc. My point is that horsepower is no more dominant than other factors that aircraft designers must consider when evaluating aircraft performance.
Tommy wrote:Again, base line poh performance numbers are what should be looked at when comparing aircraft, nothing else.
Not sure what you mean by "base line," but it's obvious that people value a lot more than just performance when comparing aircraft, e.g., safety, economy, easy-to-fly, comfort, noise, etc.
Tommy wrote:Again Dave, you continue to cherry pick performance i.e starting at 5,000' or sea level.
I was simply refuting your claim that a DA42-VI can't out climb a BE58 Baron by providing the real-world circumstances under which it did exactly that. We never tried a climb comparison at sea level, but I'm pretty sure the Baron would easily win at that altitude. If I were trying to "cherry pick," we could have performed our testing at an altitude like 10,000 feet or higher where the turbo DA42 would more easily have out climbed the Baron.
Tommy wrote:There must be a reason why the manufacturer in the poh states thats the recommended cruise setting is 75% and not 92%. If it's not necessary and poses no degradation or ill effects why is it there?
The 75% power level is not stated as a limitation, and there's no prohibition on operating at higher power levels. 75% is recommended because of the point I made earlier: Because the amount of horsepower required in cruise flight increases with the cube of velocity, increasing power from 75% to 92% doesn't result in anything close to a proportional increase in airspeed. Instead, cruising at 92% causes the aircraft to operate less efficiently, burning more fuel/mile. Consider 75% power as sort of the "sweet spot" between fuel economy vs. actually getting to your destination in a reasonable amount of time.
Tommy wrote:There isn't and airplane made out there diesel or avgas that has not had nothing but problems with gear boxes.
I guess you've never heard of Rotax airplane engines that now dominate the Experimental and/or Light Sport aircraft markets, shipping in numbers approaching those of new Continental or Lycoming engines. A Rotax engine in cruise operates at about 5000 RPM with a gearbox that lowers the prop RPM into the 2000+ range. And based on years of experience, Rotaxes are now considered to be just as reliable (if not more so) than a Continental or Lycoming engine.
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