Vyse question

[unreal]

When I did my MEI training a couple years back, it was demonstrated to me by the examiner that at higher density altitudes and lower gross weights, published Vyse (i.e. blueline) won't yield maximum rate of climb when engine-out. In fact, you could gain quite a bit of performance simply by raising the nose and lowering the airspeed by several knots.

Now, I'm curious as to why this is. Up until now, I've thought that published Vyse was based on sea-level, standard day, MGTOW. Any non-standard pressure or temperature, or anything lower than MGTOW would lower Vyse. For example, a Seminole at 9,000 feet and 3600 lbs (200 lbs less than MGTOW) would have a Vyse somewhere around 84-85 instead of 88. However, I've just received some contradictory information and would like to clear it all up. Is published Vyse actually based on what I think it is, or is it something else?

Any thoughts on this?

 

[VNugget]

I don't see the contradiction, what the examiner showed you in the first paragraph matches what you said in the second paragraph. I read it a few times over.

 

[SPilot]

http://avstop.com/AC/FlightTraingHandbook/ClimbPerformance.html

and even better:

http://selair.selkirk.bc.ca/aerodynamics1/Performance/Page10.html

 

[unreal]

I don't see the contradiction, what the examiner showed you in the first paragraph matches what you said in the second paragraph. I read it a few times over.

I don't think I asked my question correctly. I mean to ask about how Vyse is actually derived. Is it based on MGTOW, sea-level, standard day, or is it derived under different conditions?

 

[Sam Snead]

I don't think I asked my question correctly. I mean to ask about how Vyse is actually derived. Is it based on MGTOW, sea-level, standard day, or is it derived under different conditions?

I understood that Vmc was derived in standard sea-level atmospheric conditions. Would it follow that Vyse is found under the same conditions as Vmc (assuming any part of this paragraph is correct?). It seems likely.

Plus, airspeed indicator markings are meant to be used at MTOW under standard atmosphere, when the line (blue line, red line) is painted on and there is no ADC, etc. to make adjustments.

 

[VNugget]

§ 23.67 Climb: One engine inoperative.

top (a) For normal, utility, and acrobatic category reciprocating engine-powered airplanes of 6,000 pounds or less maximum weight, the following apply:
(1) Except for those airplanes that meet the requirements prescribed in §23.562(d), each airplane with a VSO of more than 61 knots must be able to maintain a steady climb gradient of at least 1.5 percent at a pressure altitude of 5,000 feet with the—
(i) Critical engine inoperative and its propeller in the minimum drag position;
(ii) Remaining engine(s) at not more than maximum continuous power;
(iii) Landing gear retracted;
(iv) Wing flaps retracted; and
(v) Climb speed not less than 1.2 VS1.
(2) For each airplane that meets the requirements prescribed in §23.562(d), or that has a VSO of 61 knots or less, the steady gradient of climb or descent at a pressure altitude of 5,000 feet must be determined with the—
(i) Critical engine inoperative and its propeller in the minimum drag position;
(ii) Remaining engine(s) at not more than maximum continuous power;
(iii) Landing gear retracted;
(iv) Wing flaps retracted; and
(v) Climb speed not less than 1.2VS1.
(b) For normal, utility, and acrobatic category reciprocating engine-powered airplanes of more than 6,000 pounds maximum weight, and turbine engine-powered airplanes in the normal, utility, and acrobatic category—
(1) The steady gradient of climb at an altitude of 400 feet above the takeoff must be measurably positive with the—
(i) Critical engine inoperative and its propeller in the minimum drag position;
(ii) Remaining engine(s) at takeoff power;
(iii) Landing gear retracted;
(iv) Wing flaps in the takeoff position(s); and
(v) Climb speed equal to that achieved at 50 feet in the demonstration of §23.53.
(2) The steady gradient of climb must not be less than 0.75 percent at an altitude of 1,500 feet above the takeoff surface, or landing surface, as appropriate, with the—
(i) Critical engine inoperative and its propeller in the minimum drag position;
(ii) Remaining engine(s) at not more than maximum continuous power;
(iii) Landing gear retracted;
(iv) Wing flaps retracted; and
(v) Climb speed not less than 1.2 VS1.
(c) For commuter category airplanes, the following apply:
(1) Takeoff; landing gear extended. The steady gradient of climb at the altitude of the takeoff surface must be measurably positive for two-engine airplanes, not less than 0.3 percent for three-engine airplanes, or 0.5 percent for four-engine airplanes with—
(i) The critical engine inoperative and its propeller in the position it rapidly and automatically assumes;
(ii) The remaining engine(s) at takeoff power;
(iii) The landing gear extended, and all landing gear doors open;
(iv) The wing flaps in the takeoff position(s);
(v) The wings level; and
(vi) A climb speed equal to V2.
(2) Takeoff; landing gear retracted. The steady gradient of climb at an altitude of 400 feet above the takeoff surface must be not less than 2.0 percent of two-engine airplanes, 2.3 percent for three-engine airplanes, and 2.6 percent for four-engine airplanes with—
(i) The critical engine inoperative and its propeller in the position it rapidly and automatically assumes;
(ii) The remaining engine(s) at takeoff power;
(iii) The landing gear retracted;
(iv) The wing flaps in the takeoff position(s);
(v) A climb speed equal to V2.
(3) Enroute. The steady gradient of climb at an altitude of 1,500 feet above the takeoff or landing surface, as appropriate, must be not less than 1.2 percent for two-engine airplanes, 1.5 percent for three-engine airplanes, and 1.7 percent for four-engine airplanes with—
(i) The critical engine inoperative and its propeller in the minimum drag position;
(ii) The remaining engine(s) at not more than maximum continuous power;
(iii) The landing gear retracted;
(iv) The wing flaps retracted; and
(v) A climb speed not less than 1.2 VS1.
(4) Discontinued approach. The steady gradient of climb at an altitude of 400 feet above the landing surface must be not less than 2.1 percent for two-engine airplanes, 2.4 percent for three-engine airplanes, and 2.7 percent for four-engine airplanes, with—
(i) The critical engine inoperative and its propeller in the minimum drag position;
(ii) The remaining engine(s) at takeoff power;
(iii) Landing gear retracted;
(iv) Wing flaps in the approach position(s) in which VS1 for these position(s) does not exceed 110 percent of the VS1 for the related all-engines-operated landing position(s); and
(v) A climb speed established in connection with normal landing procedures but not exceeding 1.5 VS1.
[Doc. No. 27807, 61 FR 5186, Feb. 9, 1996]

 

[MauleSkinner]

However, I've just received some contradictory information and would like to clear it all up.

What contradictory information have you just received? Knowing that might help answer your question.

Fly safe!

David

 

[nosehair]

...uuuh, all speeds; stall speeds, Vmc, Vx, Vy, Vyse, maneuver, best glide, etc., are based on MGTOW @ sea level. All speeds are reduced accordingly at lower weights - in light airplanes. Heavy airplanes have charts to compute these speeds. Light airplane handbooks don't, but the aerodynamics are the same. When you are significantly lighter than full weight, you should experiment with a slightly lower speed to get maximum climb or minimum descent on the VSI.

 

[Singlecoil]

Divide your current weight by your gross weight, then take the square root of that. That number becomes your conversion factor. Multiply any airspeed number (stall speed, climb speed, etc) by that conversion factor and you have your new airspeed number for that new weight.

This is how the tables of airspeeds that large aircraft use are derived.