Best rate-of-climb speed

[King Brown]

For climb test, what's your guess for the best speed for 2250-gross Bushmaster with 180hp Lycoming and McCauley 84/43 prop, please?

[Richard Deblack]

You said guess. So here it is. 65 ?

[King Brown]

Thanks, Richard. That's my guess, too. Some buddies say 70. When I get the weather, I'll post the answer here.

[aktango58]

is that 65 in a downwind turn? :P

[NimpoCub]

Airspeed, yep... but don't be lookin' @ the ground.

Here's something I've thought about but always forget to try:
Best rate of climb after the flaps are retracted is one thing, but would it help to leave 1 notch of flaps? I'm thinking that the extra lift would pull ya up quicker, but then there's the drag penalty. Anyone experimented w/that?

[King Brown]

I'm going to try one notch of flats, for sure. The aircraft is new to me; the climb test last step to restrictions-off CofA. I noticed one day, with one notch at about 400-feet, that I seemed to be leaving the water quickly and was surprised to see 900fpm without even trying.

[bob turner]

I have heard from reliable sources that drag has a negative effect on climb rate. Flaps are drag.

[Bill Ingerson]

I was playing with my cub today on the grass. Its a 150 h.p PA-18 and I always leave my flaps up then get the plane rolling, it speeds up faster without the flap drag. Once the tail is up then I give her the first notch of flaps and when I feel the plane is ready to fly I pull some on the flap and the plane just lifts off great, not full flap but past the first notch, then lower it back down to the first notch, works great, trim forward before take off and away you go. I still need to play with it more, need to learn to slow it down on landing as well. Climb out, I'm guessing 65

Bill

[skywagon8a]

I'm going to try one notch of flats, for sure. The aircraft is new to me; the climb test last step to restrictions-off CofA. I noticed one day, with one notch at about 400-feet, that I seemed to be leaving the water quickly and was surprised to see 900fpm without even trying.

You have been getting all sorts of answers none of which seem to have come from a Bushmaster owner. What is the objective of the climb test which the restrictions for your CofA are asking for? I am assuming that they want to know what the best rate of climb is? That is the most altitude gained over a period of time. This is determined by timing your climb at full power with the flaps up while maintaining a constant airspeed. Do this at several different speeds until you can determine which speed gives you the most altitude gained per minute.

[WSH]

I'm going to try one notch of flats, for sure. The aircraft is new to me; the climb test last step to restrictions-off CofA. I noticed one day, with one notch at about 400-feet, that I seemed to be leaving the water quickly and was surprised to see 900fpm without even trying.

You have been getting all sorts of answers none of which seem to have come from a Bushmaster owner. What is the objective of the climb test which the restrictions for your CofA are asking for? I am assuming that they want to know what the best rate of climb is? That is the most altitude gained over a period of time. This is determined by timing your climb at full power with the flaps up while maintaining a constant airspeed. Do this at several different speeds until you can determine which speed gives you the most altitude gained per minute.

Or, use the speed that produces the best rate on the VSI.

[marcusofcotton]

There is talk of Vy but don't forget Vx, it isn't going to be indicated by your VSI.

Mark J

[Steve's Aircraft (Steve)]

Curiosity, are you looking for the best " RATE " or the best "ANGLE " climb speeds? Normally, the best "rate" is accomplished with a minimum of drag ( flap ) and higher airspeeds. The best "angle" is usually lower airspeed with best deployment of lift enhancing devices (flaps). The best angle is used to gain the most altitude in a given distance ( to clear the treetops) where best rate is most altitude gain over time. ( to get to a predetermined altitude in the least amount of time. ) Most of the discussion seems to be related to best angle rather than best rate.

Steve

[King Brown]

A Canadian certification requirement for homebuilders is to submit a climb test report, using a graph to determine the minimum required altitude gain in three minutes for the conditions of ground level pressure altitude.

The climb test should be started as soon as the aircraft attains a state of steady climb after taking off. I believe the minimum required altitude gain is 945 feet in three minutes. It's rate-of-climb.

[HydroCub]

If you find your Lmax/Dmin airspeed, you will be on your Vy airspeed.

To find that airspeed, maintain level flight with pitch and begin to slowly decrease airspeed by reducing power.... holding altitude very precisely with pitch adjustments. At some airspeed, you will have to reverse your power (increase) as the airspeed continues to decrease. The airspeed where this reversal occurs will be very close to your Vy airspeed.

[WSH]

If you find your Lmax/Dmin airspeed, you will be on your Vy airspeed.

\


Then how do you explain the 9 mph difference between the two in a Cessna '74 182? Or any other single engine Cessna for that matter?

Best Glide(L/D max) is 80 MPH at max gross weight.
Vy is 89 MPH at max gross weight at sea level.

And, if you were to increase the amount of Hp, Vy would change, yet, L/D max would remain the same, wouldn't it?

[HydroCub]

If you find your Lmax/Dmin airspeed, you will be on your Vy airspeed.

\


Then how do you explain the 9 mph difference between the two in a Cessna '74 182? Or any other single engine Cessna for that matter?

Best Glide(L/D max) is 80 MPH at max gross weight.
Vy is 89 MPH at max gross weight at sea level.

And, if you were to increase the amount of Hp, Vy would change, yet, L/D max would remain the same, wouldn't it?

Good point. That 89 mph Vy seems high to me, but I guess it is what it is. Is the 80 mph best glide airspeed described as L/Dmax also? Most light aircraft I'm familiar with have a much closer margin between the two airspeeds... usually 1-3 mph, as I recall.

[WSH]

Actually no, "Best Glide" is what the Owners Manual references, I added the L/D max part but as I understand it, they are one and the same, aren't they?

89 mph Vy is accurate, as is the 80 mph best glide. It's my airplane!
Of course for the same type of airplane, say with less power to weight ratio, the two would be closer. It's not hard to imagine that both, Vy and L/D max, would be nearly the same, say in a 150/152.

Vy is product of excess power
Vx is product of excess thrust
L/D max is simply, the maximum amount of lift for minimum amount of drag.

L/D max is an Angle of attack speed, while Vx, Vy are not, Their angle of attack would change according to the amount of excess thrust or power that was available. The angle of attack remains constant with L/D max, however the speed changes with the gross weight

Does that sound right?

Hopefully an Aeronautical Engineer will get in here set the record straight, before this goes much further, at least on my part.

[HydroCub]

Actually no, "Best Glide" is what the Owners Manual references, I added the L/D max part but as I understand it, they are one and the same, aren't they?

89 mph Vy is accurate, as is the 80 mph best glide. It's my airplane!
Of course for the same type of airplane, say with less power to weight ratio, the two would be closer. It's not hard to imagine that both, Vy and L/D max, would be nearly the same, say in a 150/152.

In reality, there are two best glide airspeeds.... best distance and minimum sink. The 80 mph best glide airspeed seems somewhat slow to me so it might be related to minimum sink airspeed. Best distance glide airspeed and Vy would be the airspeeds that should have close values.
.

[WSH]

Actually no, "Best Glide" is what the Owners Manual references, I added the L/D max part but as I understand it, they are one and the same, aren't they?

89 mph Vy is accurate, as is the 80 mph best glide. It's my airplane!
Of course for the same type of airplane, say with less power to weight ratio, the two would be closer. It's not hard to imagine that both, Vy and L/D max, would be nearly the same, say in a 150/152.

In reality, there are two best glide airspeeds.... best distance and minimum sink. The 80 mph best glide airspeed seems somewhat slow to me so it might be related to minimum sink airspeed. Best distance glide airspeed and Vy would be the airspeeds that should have close values.
.

It may "seem somewhat slow" to you but according to Cessna, in a '74 182P, 80 MPH is "Maximum Glide(L/D max)- in Miles". The illustration/chart has nothing to do with "Minimum Sink".

Minimum Sink will usually be very close to 76% of Best Glide(L/D max), and just above stall speed or in this case, 61 MPH.

[60below]

The way I understand the question, Steve has stated the answer well.

[NimpoCub]

Best rate of climb after the flaps are retracted is one thing, but would it help to leave 1 notch of flaps? I'm thinking that the extra lift would pull ya up quicker, but then there's the drag penalty. Anyone experimented w/that?

I'm going to try one notch of flats, for sure. The aircraft is new to me; the climb test last step to restrictions-off CofA. I noticed one day, with one notch at about 400-feet, that I seemed to be leaving the water quickly and was surprised to see 900fpm without even trying.

King, did'ja ever try the difference in climb rate with/without that lil bit of flap?
I think about these things @ night when I can't sleep, but need a post-it note on the panel to remember to actually try it.

[dougc905]

The VSI will lag. Better to use your sensitive altimeter and a stopwatch.

Or, use the speed that produces the best rate on the VSI.

[NimpoCub]

How 'bout just reading the GPS? It only lags a second (refreshes), right??

Edit: It just occured to me that what I'm interested in is the best ANGLE (to clear the treetops as Steve said) so it seems that @ a lower airspeed & the VSI or GPS climb rate PEGGED, that first notch of flaps would help elevate my a$$ quicker. (& my stinky hip boots too, right behindprops?)

[Flyin S]

As I understand it, Best Glide (distance) occurs at L\D Max, but Best Rate of Climb (Vy) does not---it occurs where you have the most excess horsepower (difference between power required and power available). Both the Power Available and Power Required curves change with airspeed. Another interesting note is that Best Range Airspeed also occurs at L/D Max but will be a higher airspeed then Best Glide---because the drag characteristics of the airplane are different power-on versus power-off.

[aktango58]

Logan,

45, lots of flaps for the cub...

Feels slow, but do a few trials along the bank and see when you are above the trees... check with different settings but the same wind/temp/weight... in other words, don't be drinking a six pack from the back between trials

[bob turner]

Flaps do not lift the airplane. Excess thrust does. If you use flaps in a best angle situation, you will be climbing below the flaps up stall speed. In a Super Cub, a full flaps takeoff and climb is impressive, exhilarating and dangerous. If your engine so much as coughs in the first hundred feet or so you might lose more than a beautiful Cub. At speeds above flaps up stall, the flaps add more drag than anything else.

But have at it - we have pilots who swear the C-180 climbs better with 20 degrees of flaps at 90 indicated, and they hold that configuration almost until cruise altitude. The equations leave them unimpressed.

[HydroCub]

Flaps do not lift the airplane. Excess thrust does. If you use flaps in a best angle situation, you will be climbing below the flaps up stall speed. In a Super Cub, a full flaps takeoff and climb is impressive, exhilarating and dangerous. If your engine so much as coughs in the first hundred feet or so you might lose more than a beautiful Cub. At speeds above flaps up stall, the flaps add more drag than anything else.

But have at it - we have pilots who swear the C-180 climbs better with 20 degrees of flaps at 90 indicated, and they hold that configuration almost until cruise altitude. The equations leave them unimpressed.

There are many light aircraft operating manuals that specify the use of "takeoff" flaps for a short field obstacle takeoff, which is the only real reason to use a "best angle" procedure (Vx climb airspeed).

Last time I flew, the wings (and flaps) did lift the airplane and the thrust pulled the wing through the air. Any excess thrust simply allowed a higher angle of attack to give a rate of climb for any chosen climb airspeed. Too much flap yields drag which greatly reduces the excess thrust available. I don't know of any aircraft the should be flown "best rate" of climb with flaps, but there are many that specify a flap configuration for "best angle" of climb.

An engine failure on any SE aircraft at best angle of climb airspeed has a very high risk..... but clearing the obstacle mitigates accepting that risk if you intend to takeoff.

[bob turner]

An engine failure at Vx on a flaps up Cub is handleable. If you are under a hundred feet it will be a very firm touchdown. The Super Cub manual recommends full flaps for an obstacle takeoff. The deck angle for Vx climb in that configuration is such that you will not recover flying speed if your engine coughs. You will fall from 100 feet to the deck, and maybe hit flat. If you make it to 2-300 feet you have a chance to get the nose over and maybe flare. The chances of injury are, in my opinion, quite high.

[NimpoCub]

Keep it up you guys, I don't know much about this "max stuff" yet, so I'm just a spectator. Lovin' it tho!
As soon as the lake gets hard enough to get it up again (heh) I'll go up high & try some of this stuff.

My thought is as soon as I get over MCA @ full throttle I can start pulling up & see how she does (@ altitude of course) and then try the same thing by pulling another notch. Will be interesting, & of course not let it get near stall speed while climbing. I'd just like to get the feel of how close to a helicopter it will climb, with a bit of margin. Not something I'll do for kicks, but just to know what the climb will be with max thrust AND max lift. And the resultant drag, of course.
SOMEBODY must have experimented w/this kind'a stuff... Pireps would be better 'n opinion.

Thanks again for the good comments, keep it up!

[aktango58]

Remember, it is not how fast she goes up, but how steep.

Bob is correct, but most light birds will come down with a bend from a vx engine out.

Get to slow, and you will not climb at all. Takes practice, and find a good tall cliff you can judge your climb... Much more than 100' of vx and you might want to land other places and not need that...

[nanook]

Theory is great, it won't get you over the trees at the end of the runway though.... You use full flaps on take-off to pop yourself off of a rough, muddy or snowy surface.....you build airspeed much faster without the drag from skiis or tires on the runway surface...Nobody leaves full flaps on beyond popping yourself off the ground....you are bleeding flaps off the moment you can (to reduce drag), the last notch of flaps on a cub creates more lift than drag in a Vx climb configuration.

I would guess that a Bushmaster would be closer to what aktango58 said @45... I might go as low as 40 indicated...I have never flown a Bushmaster though, I can only relate to what an extended wing, 180hp/Pawnee prop, supercub does...if you are describing, trying to reach a minimum altitude in the least amount of time....you want to be at Vx not Vy.... The way I'm understanding this is, you only need to exceed a minimum "rate" of 315' per minute, for three minutes.... With your prop, pop that thing off the ground with full flaps, lower the nose and bleed off flaps... When the prop hits redline, pitch the nose up to keep the prop just under redline and hold it there.... You will be climbing at 1500-2000'per minute....try it with no flaps and then try it with a notch of flaps....see what your airspeed indicator is reading and record your max altitude gain for three minute climb.....

[NimpoCub]

Flaps do not lift the airplane. Excess thrust does. If you use flaps in a best angle situation, you will be climbing below the flaps up stall speed.

Not to be argumentative, but MY thought is that while thrust pulls the airplane/wings up in an angle that allows airspeed to be maintained when clean. I'm wondering if with flaps extended (whatever amount) @ a lil' less angle of attack, that thrust is still pulling me up, PLUS the lift from the flaps lifting me up.
Usually 1 + 1 = 2, but maybe not here.

Last time I flew, the wings (and flaps) did lift the airplane and the thrust pulled the wing through the air. Any excess thrust simply allowed a higher angle of attack

That's what I'm thinkin'. I won't have any "exess" thrust, it will all be used in maintaining best angle (AOA of the wing). I understand that that AOA will need be reduced by having any flaps extended, but I'm wondering if the extra lift will help the angle of climb of the whole aircraft.

An engine failure on any SE aircraft at best angle of climb airspeed has a very high risk..... but clearing the obstacle mitigates accepting that risk if you intend to takeoff.

Agree 101%, an engine out/cough is always a BadThing, low & slow. If I ever (for whatever reason) get into a spot that I feel is quite tight, I'd like to know if I'll clear that obstacle better w/without flap "help". That's all I'm wondering.

Remember, it is not how fast she goes up, but how steep.

Exactly what I've been trying to s'plain. Thanks O eloquent one!
Thanks for the thoughts & PM's, I'm looking forward to getting (way) up there, slowing to 40 w/2 notches, then full power, and when the speed starts to increase (as in just breaking water & flying), starting to pull up (avoiding a departure stall) and then trying it w/more flaps. I'm also assuming I can believe the vertical speed on the GPS.

[NimpoCub]

Theory is great, it won't get you over the trees at the end of the runway though....

the last notch of flaps on a cub creates more lift than drag in a Vx climb configuration.

That's what I wanted to hear/learn. I wanna "get the feel" of that before I (ever) need to know/use it.

[bob turner]

You can probably climb at 40 with flaps up. I do it all the time. I have had a complete engine failure at 100' and Vx, but it was flaps up.

If you want to do the Super Cub full flaps Vx climb, you will be climbing relatively slowly at an incredible angle and pretty much zero indicated airspeed. It is impressive for three reasons: it is an unbelievable deck angle, it is a potentially dangerous maneuver, and it will get you over some pretty daunting obstacles, meaning you are in a place you should not be without a death wish.

The C-180 is similar - they call for flaps 20 and a specific airspeed - I think it is 59, but not sure. At a hundred feet an engine failure might be fatal.

The Helio book says "hold the stick all the way back and prepare for airframe damage". And my limited experience in the Helio indicates that you have a lot better chance of walking away.

All opinion - but I have tried it.

[aviationinfo]

...and if you do a truly slow-speed climbout do Not look back at the tail. The shaking going on back there is probably the best reason not to make a habit of it! It's not good for the heart.

[mvivion]

Theory is great, it won't get you over the trees at the end of the runway though.... You use full flaps on take-off to pop yourself off of a rough, muddy or snowy surface.....you build airspeed much faster without the drag from skiis or tires on the runway surface...Nobody leaves full flaps on beyond popping yourself off the ground....you are bleeding flaps off the moment you can (to reduce drag), the last notch of flaps on a cub creates more lift than drag in a Vx climb configuration.

.if you are describing, trying to reach a minimum altitude in the least amount of time....you want to be at Vx not Vy.... .

First of all, the maximum altitude gained for a given period of time IS Vy, not Vx. Vx is the maximum gain in height for the minimum forward movement. I believe what the original poster is required to document is in fact Vy.

I'm guessing Piper actually flight tested the Super Cub before they put that recommendation for full flaps and 45 mph indicated for best angle of climb in the operators manual. Just a guess, though. Nevertheless, if you REALLY need to get over an obstacle without much forward motion, that is indeed the configuration and speed to get it done.

Is that dangerous? That's relative. I find it interesting that so many folks are so worried about their engine quitting on takeoff, yet they'll happily fly over country all day long where the likelihood of a safe landing in the event of engine failure is low. And, a long thread lately on water skiing....wouldn't an engine burp whilst doing that be a bit....wet??? How often do catastrophic engine failures occur in these things, after all? Actually, only for the sake of discounting a procedure one doesn't support, it seems.

Now, don't get me wrong--I'm not a big fan of using that technique close to the ground any more than the next guy, but it IS the recommended best angle of climb configuration provided by Piper.

For the "heavier" aircraft out there, note that the CC-18 does NOT recommend full flaps OR 45 mph as best angle configuration. Of course, that's a 2300 pound airplane, NOT a 1750 pound one. Go figure.

Aerodynamics....ain't it grand?

MTV

[aktango58]

Let me see if I can recall, Vx goes up as DA increases, Vy decreases as DA increases, (Density altitude)...

The heavier the bird, the faster each speed must be to compensate for the extra weight...

MTV, thank you.

[bob turner]

Of course the danger is relative. I have flown over things I could not land on. My only catastrophic engine failure was in cruise. But the hiccups seem to occur on lift off, and all it takes is a hiccup if you are pointed straight up. I do demonstrate these things once - and we take the Cub up to altitude and point it up at full power to see what it will do. I do not have the skill to look at the tail feathers when hanging on the prop at extreme deck angles.

One of the fun things I did as a 737 driver was get the chance to give a check airman a catastrophic engine failure just as he reached the 28 degree deck angle. He had no idea I was a simulator type, and was not expecting it. He was a very good pilot, and barely survived the cut.

I have no idea what the deck angle is on a Cub with full flaps, Vx, but I can tell you it is a lot higher than 28 degrees - at least with 160 hp and a Borer.

[texmex]

Another interesting note is that Best Range Airspeed also occurs at L/D Max but will be a higher airspeed then Best Glide---because the drag characteristics of the airplane are different power-on versus power-off.

What was the difference between piston engine and jets re this topic???

Timely thread as Im in the process of dusting off the books for an interview. I just get distracted by this web site which is a lot more interesting.
I hope you have the answer you sort King Brown.

[nanook]

If you are told that you must reach a minimum altitude in order to pass certification and you have three minutes to get there, what climb profile are you going to use?