Many pilots with complexes about their flying were neglected in the infancy stages of training. The roots of poor flying performance can often be traced to misconceptions about Exercises Seven and Eight, or Lesson Four dealing with climbing and descending. Test candidates and underperformers may conceal such handicaps behind charades or resignation. The rather sincere explanations may vary: "I realize I should fly more regularly,", or: "I can't believe I've botched the landing (or forced landing) again." Or worse: "My instructor never taught me." Especially the last expression, often heard after bumpy landings, poor performance in competitions or even a botched forced landing, sadly sometimes rings true.
Poor performers at times show inventive ways to "work around" carried handicaps and "inherited" shortcomings."Work-around techniques" may involve minute tough rapid and incessant aircraft nose attitude or power changes during the climb, cruise or the approach to land. Some have to work hard unnecessarily during the approach to land to carry out consistently safe landings. Some even resort to cross-controls, though this may be subtle. Trimming and balance is crucially important and can make hundreds of fleet difference in terms of both distance and height.
During corrective training an instructor invariably revisits the principles and graphs on climbing and descending. The flip-side of the coin is that pilots doing well in, for example, a flying rally or gliding championships, invariably grasp the differences between flying for range or endurance, gliding angles and speeds, etc, to effectively use these to their advantage. The lesson on climbing and descending naturally flows from the preceding lesson on straight and level flying. Similar fundamentals apply.
This series is not intended to rewrite or substitute the basic lessons. The objective is rather to focus on common mistakes and perhaps add value. A proven technique in critical-analytical flying instruction to find and eliminate inherent shortcomings is to, after a botched exercise, bite ones lip while patiently allowing a student or test candidate to first reveal his or her depth of understanding upon retracing an exercise with the aid of sketches or graphs. The overall idea is to add value, proficiency and safety.
The exercises on climbing and descending on face value appear to be mundane. Sometimes these are incorrectly merely incorporated as part of ab initio flying training along with other exercises .But the exercises need to be consolidated and, if necessary, repeated at the earliest possible stages, lest the cracks show up sooner rather than later. Many pilots do not associate or correlate aircraft nose attitude with a range of speeds, or their particular relevance and importance to a specific flight regime. A common misconception, for instance, manifests itself during forced landing exercises when the glide is futilely attempted to the ‘stretched.'
In Mechanics of flight (pitman: 1972; pp.188-195) A.C Kermode explains how, during a powerless glide, the lift and drag vectors set up a total reaction to balance weight. Lift acts perpendiculars to the flight path. The total reaction acts perpendicular to the earth's true horizontal plane. This angle during a glide corresponds to the angle between the respective total reaction and the lift vectors. The actual gliding angle would correspond to the angle between the aircrafts flight path and the earth's true horizontal.
Gliding efficiency in terms of range is dependent on the gliding angle which, in turn, depends on the value of the lift/drag relationship. Therefore, if the aircraft is to optimally extend gliding range, the value of lift/drag must be a maximum .As it is virtually impossible during a glide to judge the angle of attack or to visualize the optimum lift/drag relationship, which will achieve the "flattest" possible gliding angle for best range, the pilots only resort is to know the best average speed from the aircrafts flight manual.
But, the best gliding speed (especially in heavier aircraft) may vary with centre of gravity and weight changes. The explanation is by no means redundant. Trying to "flatten" the glide to gain range simply does not work for the aforesaid reasons.
The total drag graph holds the key to better in-depth understanding .If the nose attitude is flattened, the speed reduces into the low speed drag range .Induced drag, or lift dependent drag (according to different schools of thought) comes into play. Conversely, if the nose is lowered the gliding range is similarly reduced as profile drag increases, despite the extra speed.
Lift will now increase as speed increases, although the total amount of drag may be the same as at lo speed .(Remember the gliding range depends on lift/drag value).But ,during a transitional phase ,as angle of attack is decreased, the value of lift/drag is increased.
The objective of a powerless glide as applied to a forced landing is mostly to land at the lowest possible ground speed, reducing kinetic energy. Many pilots and even instructors tend to dig up the sketches for gliding with and into wind to explain gliding angle to distinguish between real and apparent gliding range.
This is not incorrect or inapplicable, but the gliding angle discussed above pertains to effective aerodynamic forces and should not be confused.
When considering groundspeeds (gliding against and into wind) a simple sectional trigonometry construction of the velocity vector triangle should show an increase on the slanted or hypotenuse side will correspond to both increases in the vertical and horizontal sides. To reach a specific touchdown point, any advantage gained on the horizontal will have an associated increase in the vertical, or descent ate.
In a power-assisted descent a useful rule of thumb based on the "one in sixty rule" on a three degree slope is to multiply ground speed by five to find required rate of descent, or to multiply height in thousands of feet by three to find the range or distance out in nautical miles- that is, if established on a stabilized approach on the glide slope at the proper approach speed.
The application are marvelous to observe in practice .The various options and varying results are extensive and put the "art" back into flying when practiced .It even gives one the edge in competitions. So, please do not indulge in expressions of deviant, dangerously low or extreme flying when cut loose into the wild blue yonder.
Rather become involved in rally or competition flying, or if just going for a flip, perhaps practice a few forced landings. Not only will it make one more proficient, but safer.
Equally amazing is how the forces of physics always attempt to achieve a balance, in the pure glide or power assisted descend the lift and gravity (weight) vectors set up a resultant vector supplying ‘weight apparent thrust' along the glide path. Truly amazing!
Editorial space restrictions always apply in series like these. Much, much more can be said about descending and powerless glides. I will suffice to state that if skimming over these exercises initially, one is being deprived and the discrepancies will show up later.
Pertaining to climbing, a common misconception is that an aircraft climbs once the lift vector is greater than weight. Once again in powered flight the total drag curve and power required graphs apply.
Optimum performance would depend on the maximum difference between power required and that available .At first glance this may be axiomatic, but with respective engine and propeller efficiency ranges, the effective overall performance parameters vary.
Flying initially in a little trainer, it may be hard to imagine life and death decisions may later depend on understanding these basics. Especially a heavily loaded twin aircraft will one day either clear an obstacle or not, depending on understanding these efficiencies and where the best rate of climb on either both or a single engine would lie on the graph.
The relative drag forfeiture and proportional overall performance gained may one day make the difference between safe or insufficient fuel reserves.
So, next time you adhere to the acronymic attitude (lower) ,speed (increase) ,power (reduce to cruising power) and trim (ASPT) leveling off technique, consider how the aircraft is traversing through and along adverse to optimum points on the total drag and power required graphs.
Conversely, the sequence for commencing a climb from level flight or PAST, that is: power (increase), attitude (raise nose), speed (adjust for best rate or maximum angle) and trim for attitude, power setting and balance will always apply throughout a flying career.
Explore these climbing regimes and you may, for example, find how the rate of climb on a Piper Arrow 111 is virtually the same at 80 knots and 103 knots, or how a light twin on one engine descends at ten or more knots below blue line (best single engine rate of climb speed) and actually climbs with a lower nose attitude at blue line speed.
This may be very hard to believe at low level with on engine feathered and power lines straight ahead .But, do make sure you understand these principles thoroughly and hopefully one day live to tell how it made the difference between life and death!
