Talk:Cumulonimbus and aviation

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Commercial aviation[edit]

"Heavy transportation airplanes may occasionally have to cross a thunderstorm line associated with a cold front or a squall." They do it all the time.

"They may not be able to overfly the cumulonimbus, because at 36000 feet, the aircraft may be in or near what is known as the coffin corner (stall speed = Vne), thus making it structurally dangerous to climb higher."

Why 36,000ft? It really depends on the aircraft type.

"However, some cells can rise to 70000 feet."

Where is the source for that fact? It is not in Robert Buck's book.

"Another option would be to navigate around the cells. This is strongly discouraged, however, because in the opening, new cells can grow very rapidly and engulf the aircraft.[31]"

In this part of the cited book, the author describes a hypothetical situation where a general aircraft flying around 10,000ft would face a line of thunderstorms. The author continues, showing that if you cannot pass through a gap in the line quickly you may be engulfed by rising cummulus clouds, which can lead to hazardous situation if you don't have enough stall margin (aka: too high).

"Whenever an aircraft moves to the west and crosses a thunderstorm line, the pilot will first encounter a line of powerful and laminar updraughts (that are not thermal but dynamic). The pilot should refrain from pushing the stick to try to maintain a constant altitude (similar to mountain waves), because pushing the stick can cause his airspeed to increase to the point of hitting the yellow arc (on the airspeed indicator). An airspeed this high is not permissible in turbulent conditions and may lead to break-up of the aircraft.[31]"

Nothing like that is in the cited book. Furthermore, when an aircraft moves to the east, does anything change? And, heavy transport aircraft got no yellow arc in the airspeed indicator, only general aircraft do.

"Indeed, when the pilot exits the updraught zone, he will encounter very strong turbulence due to the shear between rising and sinking air. If the airspeed is too high at this point, the airplane will break apart. The crash of Flight AF 447 is indirectly related to this situation: the pilot, being short on fuel, opted for the shortest path while crossing the thunderstorm line associated with the intertropical convergence zone, and the pitot tubes iced over. What followed is known."

A citation from an aerodynamics book and from the AF447 final accident report would be necessary here.

"On-board radars can be deceiving."

Again, a citation is needed for that claim.

"Hail shafts generate weak radar echoes and are significantly more dangerous than cloudbursts."

Dry hail is not a good reflector for radar energy, but wet hail is the greatest reflector. And Robert Buck's book talks nothing about how airborne weather radar works.

"Close to the ground, heavy rain (or snow at altitude) tends to dampen turbulence (it is said that when rain comes, most of the danger is gone). So a counter intuitive recommendation exists: it is better to fly toward the zone of heavy precipitation or toward the darkest area of the thunderstorm line.[32]

This recommendation contradicts the usual use of on-board radars to avoid areas of strong precipitation, which is usually the best course of action. There is no "miracle" solution, and the best option is to avoid these thunderstorm systems by having enough fuel on board, thus reducing the temptation to take a more dangerous route in the interest of fuel savings."

"Also, St Elmo's fires while flying inside cumulonimbus can burn out the on-board electronic equipment and even pierce a wing by melting the metal skin.[32]"

Again, nothing like that is written in the book. In page 267, Robert Buck discusses about electrical discharges in the form of lightning, not St. Elmo's fire, which is harmless.

A good source on storm avoidance can be found in Skybrary (https://www.skybrary.aero/index.php/Weather_Radar:_Storm_Avoidance) or the Airbus Briefing Note in Optimum Use of Weather Radar.177.143.47.97 (talk) 23:44, 31 October 2018 (UTC)[reply]