Multi-Engine: Zero-Sideslip
The zero-sideslip is necessary for a pilot to maintain control of an aircraft and have the greatest climb performance during an engine failure in a twin.
Aerodynamics | February 10, 2022
A v-speed is an airspeed designed for specific aircraft maneuvers in particular configurations (such as the landing configuration.)
Below are some of the most common types of airspeeds for single-engine and multi-engine aircraft.
Vso is the Stall Speed in the Landing Configuration. Vso, marked by the bottom of the white arc on the airspeed indicator, is the stalling speed or the minimum steady flight speed in the landing configuration.
In small aircraft, this is the power-off stall speed at the maximum landing weight in the landing configuration (gear and flaps down) at the most foreword center of gravity.
Vs is the Stall Speed in the Clean Configuration. Vs, marked by the bottom of the green arc on the airspeed indicator, is the stalling speed or minimum steady flight speed obtained in the clean configuration.
For most aircraft, this is the power-off stall speed at the maximum takeoff weight in the clean configuration (gear up, if retractable, and flaps up).
Vs1 is the Stalling Speed or Minimum Steady Flight Speed Obtained in a Specific Configuration.
For most aircraft, this is the power-off stall speed at the maximum takeoff weight in the clean configuration (gear up, if retractable, and flaps up). However, instead of being labeled as "Vs1 ", aircraft manufacturers label it as "Vs. "
Vr is the Rotation Speed. Vr, which is usually only displayed on glass cockpits as a "bug," is the speed at which the pilot makes a control input, intending to lift the airplane out of contract with the runway or water surface.
Regulations state that Vr cannot be less than Vs1 to reduce the possibility of an inadvertent stall during takeoff.
Vx is the Best Angle-of-Climb Speed. Vx, which is usually only displayed on glass cockpits as a "bug," is the speed that results in the greatest gain of altitude in a given horizontal distance.
In other words, this speed allows an aircraft to gain the most amount of altitude in the least amount of distance across the ground.
Pilots use Vx during short-field takeoffs, especially for clearing obstacles in the departure path.
Vy is the Best Rate-of-Climb Speed. Vy, which is usually only displayed on glass cockpits as a "bug," is the speed that results in the greatest gain in altitude in a given time.
Otherwise, put as the speed that will result in an aircraft gaining the most altitude in the least amount of time.
Vy is the "standard" airspeed to establish during the post-takeoff climb and departure phase of flight.
However, some manufactures may recommend a slightly faster airspeed to promote engine cooling while still achieving a relatively quick climb rate.
Vbg, or Vg, is the Best Glide Speed. Vbg, which is usually only displayed on glass cockpits as a "bug," is the speed that results in the most amount of lift for the least amount of drag.
In practice, this airspeed will allow an aircraft to glide the furthest distance across the ground for any given altitude. Therefore, this speed is critical for navigating an aircraft to a suitable landing site should an engine failure occur.
Vfe is the Maximum Flap Extended Speed. Vfe, marked by the top of the white arc, is the highest speed the aircraft can be flown with flaps extended without damaging it.
Typically flaps are deployed in increasing increments from retracted to fully deployed. On some aircraft, specific increment settings require slower airspeeds. Therefore multiple maximum flap extended speeds may be published for particular flap increments.
Va is the Design Maneuvering Speed. Va is usually never marked on any airspeed indicator but instead place carded in the cockpit. Va is the maximum speed at which the structural design's limit load can be imposed (either by gusts or full deflection of the control surfaces) without causing structural damage. Multiple published maneuvering speeds for a specific aircraft are common due to maneuvering speed changing as the aircraft's weight changes.
Many pilots have a general misunderstanding of the design maneuvering speed (VA), and the extent of structural protection that exists when operating an aircraft below its published Va. Va is a structural design airspeed used in determining the strength requirements for the aircraft and its control surfaces. These structural design requirements do not protect an aircraft if the pilot commands multiple control inputs on one axis or control inputs in more than one axis. Even if flying below Va.
Vno is the Maximum Structural Cruising Speed. Vno, marked by the bottom of the yellow arc on the airspeed indicator, is the speed that should not be exceeded except in smooth, non-turbulent air and then only with caution.
Flying above this speed in turbulent air can potentially cause structural damage to the aircraft.
Vne is the Never Exceed Speed. Vne, marked by a red line on the airspeed indicator, is the speed that should never be exceeded in any operation.
Going past this speed can, and will, result in structural failure of the aircraft.
Complex and multi-engine aircraft use all the v-speeds common with single-engine aircraft and add on the additional v-speeds:
Vmc is the Air Minimum Control Speed. Vmc, marked by a solid red line (not to be confused with Vne), is the calibrated airspeed at which, when the critical engine is suddenly made inoperative, it is possible to maintain control of the airplane with that engine still inoperative and maintain straight flight with an angle of bank of not more than 5 degrees.
This airspeed is subject to change drastically if current flying conditions do not match the certification conditions listed under 14 CFR Part 23.
Vlo is the Maximum Landing Gear Operating Speed. Vlo is the maximum speed at which the landing gear can be safely retracted or extended. Vlo is usually never marked on an airspeed indicator but rather place carded in the cockpit,
Depending on the aircraft, the maximum speed for landing gear retraction and extension can have different listed values.
Vxse is the Best Angle of Climb Speed Single Engine. Vxse is the airspeed where should an engine failure occur will give the most amount of altitude gained for a given distance across the ground with only one engine operating.
Vxse is usually never marked on the airspeed indicator or place carded.
Vyse is the Best Rate of Climb Speed Single Engine. Vyse, marked by a blue line on the airspeed indicator, is the airspeed where should an engine failure occur will give the most amount of altitude gained for a given amount of time.
Suppose a climb is not possible due to environmental factors. In that case, this speed will give the least amount of altitude lost for a given amount of time.
