Can a Cessna 172 fly upside down?

UL flight instructor

The second part of the blog miniseries is about everything that is not normal. These are short, crosswind and sometimes tailwind starts.

For those who have only started on asphalt up to now, grass, gravel or dirt tracks are a new experience. But before we start, an extra section on what must not happen under any circumstances:


Stable climbing

Why the constant admonitions to pay attention to the speed and prefer to start with a little more reserve? Because it's a good rule of thumb for preventing stall. Of course, it is not the speed but the angle of attack (AOA for short) that is responsible. And it is the climb that requires more lift and consequently a higher angle of attack. Unfortunately, however, the higher the angle of attack, the greater the resistance, with the unattractive side-effect of the decrease in speed. As long as neither stall warning nor AOA display are part of the mandatory minimum equipment of an aerial sports device, the only indication left for a pilot is therefore to look at his speed display.

PPL users who have previously relied on the squeaking of a stall warning in a Cessna & Co have to do without warning in the UL. To put it bluntly: if you get into a stable close to the ground, the cards have been placed for you. Therefore, the best way to avoid accidents is not to let it get that far in the first place. That sounds wonderfully simple and logical, but considering the many "contributing factors" it can be more difficult than expected.

A basic distinction is made between three types of barn:

  • A departure or power-on stall. Usually in a climb after taking off with full engine power.
  • The arrival or power-off stall. Mostly when turning into the landing approach with or without engine power.
  • The accelerated stall or dynamic stall. A stalled condition that can result from abrupt rowing movements at higher speeds.

We are interested in the departure or power-on stall. The favorable factors are:

  • Uncontrolled flight position (e.g. due to excessive pulling on the elevator, pushing flight status due to incorrect rudder and aileron use)
  • Propeller effects (torque, P-factor, corkscrew)
  • Wrong trim settings
  • Incorrect loading (heaviness) or overloading (!)
  • Too early or abrupt retraction of flaps
  • Too early / too deep turning into the transverse take-off
  • Too steep curves (high bank) without speed increase
  • Starts with a tailwind
  • Distractions, human factors

Each point offers space for full-page designs, examples and details. Therefore I leave it at this list and would like to emphasize only the last point "Distractions".

A little thing - an unusual noise, the rattling of the still open fuel filler cap, the open cabin door - all that is enough to pull pilots out of their comfort zone and distract them from flying. Unfortunately, the start is a critical phase of the flight that leaves little to no leeway for distractions and wrong decisions.


The underground

Let's start on grass, gravel or dirt roads. The latter are more likely to be found in the regions south of the Alps. With us, grass slopes predominate. The number of pilots who, according to my observation, had no contact with them during their training is frightening. A deficit with deeper psychological consequences. So everything beyond a paved slope is feared across the board. Instead of the completely unscrupulous meadow, which may even enable a restart, the paved road with a worse obstacle situation and higher risk potential is preferred for an emergency landing.

While the condition of asphalt or dirt roads is easy to see, this is unfortunately not always the case on grass roads. The legacies of a herd of wild boars are not treacherous - they are quickly discovered from the ground and from the air (thank you for the pictures and at the same time pity for the ruined slope to the LSV Hünsborn).






It's the inconspicuous bumps, holes dug by dogs or wet and soft spots. If you are the first to start in the morning, you are acting cautiously if you prefer to walk down a grass runway. There should be so much time and at the same time it is an ideal opportunity to mentally prepare for the day or flight. In any case, more time should be planned for pre-flight checks when taking off on unpaved runways and after landing for cleaning and checking for damage. Neuralgic areas are prop, brakes, landing gear, oil cooling and all screws and fixings. Or who checks the two screws on the inside of the chassis where the bike shoes are attached on a C42? Experience has shown that these tend to loosen up with constant load on unpaved slopes.

The next important point is the take-off route calculation. Sounds more complicated than it is and is mostly taken lightly by UL pilots. In a UL, we are usually in the air after 150-200 meters. However, factors such as overloading, soil conditions or “hot & high” also play a role here. A somewhat older but still readable FSM Safety Notice 3/75 summarizes the most important factors. On this basis, a few months ago I created a small web app to calculate the take-off distance.

A cowl-flap or carburetor preheater should remain closed on stony ground during taxiing and take-off if the openings point downwards and there is a risk that dust or stones could get into them. Once in the air, they can (and should!) Be opened again. Turbo engines or thermally unfavorable designs that need a lot of cooling are particularly problematic. It goes without saying that the temperatures are kept in view at take-off and during the subsequent climb. Higher speeds and a flatter ascent have a positive effect here in so far as an engine is better cooled.




Finally, an inconspicuous point that can unfortunately quickly become a problem on unpaved slopes: suction cup mounts for the digital helpers in the cockpit. In my personal opinion, suction cups have no place in a panel or on a windshield. Charging cables flying around freely on cigarette lighter adapters should also be mentioned in the same breath. The vibrations of an unpaved runway cause it to fall off sooner or later or worse: Pendulum back and forth in the panel while still hanging on the charging cable and adjust electrical main switches or even magnets. Do we remember the point “distractions” discussed above in a critical flight phase?




In professional aviation, people rightly speak of a “sterile” working environment below FL100. Of course, the workload there cannot be transferred 1: 1 to us hobby pilots, but the basic idea behind this rule counts here. Anyone who sits in the chaos full of distractions in a critical flight phase can only be on the subject to a limited extent, think in a structured manner and follow clear processes.


The take-off run

Basically every start on unpaved ground is a short start. The goal is to get off the ground as quickly as possible. Every unnecessary blow and bump goes to the material. The nose wheel suffers the most. All tailwheel flyers can now lean back and relax and skip the next sections.

A nosewheel can be relieved of pressure by pulling the elevator fully back while taxiing. This also reduces the rolling resistance at the same time. After rotating, the decisive factor is the balance and further acceleration on the main landing gear in order to then lift off in the ground effect. This is where the right flap setting comes into play. For most designs, the flaps are extended to allow them to get off the ground quickly. The crucial question is always full or only partially extended flaps. The respective operating manual of the sample gives the solution. Typically, most ULs start with the doors partially extended.

Nevertheless, some like to start with full flaps and mean to use a short start technique. This is unfortunately not the case. And what still works with good-natured and simple models like a C42 can quickly end in an accident with a high-performance model. Full flaps serve less as a buoyancy aid and more as a brake flap. Changes in the flap setting often go hand in hand with trimming and this is avoided whenever possible near the floor. An additional danger threatens the rapid crossing of the white arc. This marks the speed for the maximum extended flaps on the speedometer. If the flaps are only partially extended, it is not a problem to exceed them slightly. The assumption that it also applies to fully extended flaps is unfortunately wrong.

But what happens if the flap speed is exceeded when the flaps are full? With a C42 (!) Comparatively little. Usually there is a loud bang and the flaps jump back in by themselves. But this has enormous effects near the ground. There is a risk of sagging, impact and rollover or, with a high angle of attack, the dreaded power-on stall.


Short start technique

The most widespread "Hannemannsche" short start technique for a C42 begins at the very end of the track with holding the brakes under slow full throttle. Only after 1-2 seconds do you release the brakes and accelerate forward like in a catapult. If the flaps are partially extended, the take-off run is similar to taking off from an unpaved runway. After rotating, however, at the earliest at Vs - due to the approval for all ULs with MTOW 472.5 kg at 65 km / h - the full flaps are pulled and held tight with the hand. This creates a powerful upward impulse so that the main landing gear is also clear of the ground. Now it is a matter of carefully retracting the landing flaps in a controlled manner in conjunction with the elevator and landing flaps and with a steady increase in speed without losing altitude or touching down with the main landing gear. If you go from the ground effect to the climb without accelerating at stall speed, you will fall on your nose. In a flat climb, you can then leave the runway as usual at a safe 120-130 km / h. With this short take-off technique, a C42 can take off in just 60 meters. That would be about half the length of a football field. If you want to take it to the extreme, you can shorten your take-off run with a rolling start by turning in the start direction with the initial swing directly from the roll stop. Alone and with little fuel, take-off distances of just 50 meters are possible.

It goes without saying that this method only works on designs with manually adjustable landing flaps. You should also train with a flight instructor on a sufficiently dimensioned space before doing the freestyle on 250 meter short glider airfields. Anyone interested in such safety training can find out more at ul-fortbildung.de.


Start in cross and tail wind

Last but not least: take-offs in different wind conditions. Of course it is desirable to start against the wind. But the world is not perfect and most of the time the wind comes somehow cross from the side. Here the first thought should go to the maximum crosswind component in the operating manual. In the second thought, everyone should then ask themselves whether they are able to fly the number demonstrated by a test pilot. Who doesn't know the powerless feeling of being relegated more and more during the take-off run?

The solution here is to rotate as quickly as possible and get off the ground quickly. Quickly in the sense of in one go and not in the sense of early. As long as the departure baseline can be held with the rudder or the controlled nose wheel, this advantage should be used for as long as possible. This is especially true for patterns with elongated noses or small rudders. A DV-1 Skylark, for example, must always be prevented from flying in cross winds with a slight force - if the rotation is to be delayed as long as possible. It must always be ensured that the luv-side surface is not raised.

Once in the air you have to point your nose in the direction of the wind. If you take off with a 10-15 degree windward angle while maintaining the centerline, you have successfully mastered the crosswind.

How does it look with a tail wind? Are there situations where a UL pilot has to expect a tailwind? Yes, there are such situations. At our place, for example, the south wind flows around an 80 meter high ridge from both sides into the Ruhr valley. This results in strange pictures when the windsock shows a tailwind at the beginning of the slope and a headwind at the end. And as soon as you are out of the Ruhr valley over the mountains, the wind comes from the right. Additional turbulence and rotors on the slopes and transition areas prove to be problematic. Turning into the cross take-off should therefore not be done too early and under no circumstances should it be in the lee of the mountains. Those who fly here with sufficient speed reserves have nothing to fear.




Another situation arose during my time on Lüli. Funeral ceremonies were often held here at the nearby cemetery, which made a start against the wind less advisable for reasons of noise protection. In this case we started with a tailwind in the opposite direction. Basically for an overpowered UL with a sufficient slope length (950 meters) and little wind no problem as long as the tail wind is added as a reserve.

We come to the end of my little miniseries. In view of the many accidents with stalls close to the ground, I would like to appeal to my fellow pilots to sharpen all of their senses when taking off, not to be distracted by flying and to work with generous safety reserves and surcharges.


With this in mind, safe flies!
Your Tomas Jakobs

Tags: start technique, training, wind gusts, short start technique, decision making