Glide Performance
Expected Glide Performance drives airfield suitability decisions and impacts the conduct of the approach and landing.
Introduction to Glide Performance
- Expected Glide Performance drives airfield suitability decisions and impacts the conduct of the approach and landing.
- Ultimately, glide performance translates into options for gliders or aircraft in the event of an engine-out situation.
- Test your understanding of Glide Performance by completing the knowledge quiz, applying your knowledge in the interactive scenario, comparing your performance against the applicable Airman Certification Standards, and concluding with the topic summary to reinforce the key concepts before moving on to the next lesson.
Glide Performance Key Highlights
- Glide performance describes the aircraft’s ability to maintain distance and control while descending without engine power.
- Best glide speed provides the maximum glide distance for a given aircraft weight and configuration.
- Glide ratio compares horizontal distance traveled to altitude lost during a glide.
- Aircraft weight affects glide speed but does not significantly change the glide ratio in still air.
- Wind conditions influence actual glide distance over the ground and should be considered during emergency planning.
- Improper aircraft configuration, excessive drag, or uncoordinated flight can reduce glide performance significantly.
- Best glide speed typically increases as aircraft weight increases.
- Pilots should establish and maintain best glide speed promptly following an engine failure or power loss.
- Terrain, obstacles, and landing area selection are critical considerations during glide operations and emergency descents.
- Understanding glide performance improves emergency preparedness, decision-making, and forced landing outcomes.
Best Glide Versus Minimum Sink
- The best glide speed provides the greatest distance for the least altitude lost.
- Minimum sink speed provides the most time.
- Pilots can achieve optimal glide performance only when they correctly configure the aircraft for the best glide/minimum sink.
Glide Ratio
- The glide ratio is the ratio of the distance an aircraft travels to the altitude it loses.
- An aircraft that travels 50' horizontally for every 10' of vertical altitude is said to have a glide ratio of 5 (50/10).
- Factors that impact glide distance include wind, configuration, and technique (i.e., pilots must avoid uncoordinated flight, which increases drag and reduces glide distance).
- The best glide distance occurs at the lift/drag max where induced and parasite drag are at their minimum (equal).
Glide Performance
- An aircraft with a glide ratio of 5 has a descent angle of 11+ degrees, meaning if you lose an engine on a 3° glide slope, you cannot reach the runway, regardless of altitude.
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Effects of Winds:
- Headwinds decrease glide distance, as the aircraft has a reduced ground speed (the wind is pushing against the aircraft).
- Tailwinds increase glide distance, as the aircraft will maintain a higher ground speed (the wind is pushing the aircraft forward).
Calculating Best Glide Speed
- Refer to POH for the best glide tables.
- Note the best glide is at the highest lift-to-drag ratio, roughly halfway between Vx and Vy.
- As an aircraft becomes lighter (i.e., as an aircraft burns fuel), the best glide speed reduces as well.
- Manufacturers typically publish the best glide for a given gross weight, and the best glide will decrease as the aircraft's weight decreases.
- Pitch for best glide by controlling the nose to achieve the published speed.
- Without the published speed, point the nose in such a way as to keep the wings level; you may even need to pitch up.
- Several single-engine twins can achieve the best glide speed by applying full nose-up trim.
- No matter the technique, be mindful of stall conditions.
Calculating Minimum Sink Speed
- The minimum sink may not be in most POHs, but it is generally slower than the best glide speed.
Avionics and Electronic Flight Bag Tools
- Some avionics and EFBs provide glide rings based on the (albeit limited) flight conditions.
- These range rings are estimates only.
- Setting avionics ranges to the anticipated glide distance also provides an idea of the available options (i.e., if no airports are within that distance, any need to land will be off-airport).
Glide Performance Interactive Scenario
Interactive Scenario
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Decision 1
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Glide Performance Knowledge Check
Choose the knowledge check that matches your current training for Glide Performance.
Private Pilot
PPL knowledge check
Core Knowledge Review
Review foundational knowledge, key concepts, and practical considerations. Topic: Glide Performance.
- Immediate feedback
- Answer explanations
- Account progress tracking
Commercial Pilot
CPL knowledge check
Advanced Application
Apply knowledge to advanced operations, risk management, and aeronautical decision-making. Topic: Glide Performance.
- Immediate feedback
- Answer explanations
- Account progress tracking
Why Take a Quiz?
Quizzes reinforce key concepts, identify knowledge gaps, and build confidence for real-world decisions. Quiz material is representative of the information provided here and is not based on or sourced from the Federal Aviation Administration test bank.
Glide Performance Conclusion
- As a rule of thumb, any aircraft should be able to glide to a distance of approximately 45° down.
- If, when gliding, the point of intended landing is moving higher in the windscreen, the aircraft will land short of the intended point.
- Understanding glide performance is a regular part of flying a glider.
- What's not so normal is considering how it applies in a powered aircraft when the power is no longer there.
- Understanding glide mathematics helps pilots make faster and more accurate emergency landing decisions.
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