I was watching this video where he mentioned that a plane went around on hard touchdown. This isn't the only instance I have seen where they do this.
So, why do they do so? Isn't it a loss of profits for the airline?
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1$\begingroup$ Just s a note, it might be better to ask about a bounce after touchdown, a plane can make a (relatively) hard landing without bouncing, deliberately, if runway conditions require that. This technique is called "positive landing", and it will surprise the passengers if the pilot does not inform them of that before. $\endgroup$– Jpe61Commented Aug 8 at 20:40
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$\begingroup$ Thanks for the reply @Jpe61 but I was unable to get what you meant to say. $\endgroup$– Sambhav KhandelwalCommented Aug 9 at 12:17
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$\begingroup$ A hard touchdown does not usually lead to go around but a bounce (like the one shown in your video) does, or at least it shoul, as explained in the answers. $\endgroup$– Jpe61Commented Aug 9 at 12:31
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$\begingroup$ For what it's worth, violations of safety that lead to accidents are much larger losses to the airline. It is much cheaper to go around than pay for the consequences of even the least damaging accident (many listed in the answers below). $\endgroup$– Stephan SamuelCommented Aug 9 at 17:53
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3 Answers
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Tail Strike
In larger commercial airliners such as the Airbus A320 series, Boeing 737, or similar, a hard bounce during landing significantly increases the risk of a tail strike.
After a hard bounce, these aircraft tend to sink rapidly due to the low airspeed. This can create a sensation of the aircraft "falling," which may instinctively prompt the pilot to pull back on the controls. Alternatively, the pilot may just keep adding back pressure to the controls which they started during the flare, whereas the correct technique is to hold the landing attitude1. In both cases, doing so reduces tail clearance and increases the likelihood of a tail strike.
According to the Boeing 737 Flight Crew Training Manual (FCTM):
If the airplane bounces during a landing attempt, hold or re-establish a normal landing attitude and add thrust as necessary to control the rate of descent. Thrust need not be added for a shallow bounce or skip. If a high, hard bounce occurs, initiate a go-around.
Tunisair A320 bounce with tail strike
Austrian A320 bounce with near tail strike
For the Boeing 737, this situation is further complicated because the initial bounce may have occurred due to the thrust being higher than idle, which can cause the speedbrakes to not actually deploy on touchdown. If the thrust levers are then retarded to idle during the bounce, automatic speedbrake deployment can occur. This leads to a loss of lift and a nose-up pitching moment, potentially resulting in a tail strike or a hard landing on the subsequent touchdown (Boeing FCTM).
“Porpoising”
For other aircraft types, such as high-wing turboprop aircraft, a bounce can cause these aircraft to be more prone to "flying again" after a bounce. The danger here lies in the pilot's potential reaction to push the nose down to force the aircraft onto the ground, which could lead to "porpoising" or a hard impact on the nose gear (or even the propeller itself on light aircraft). Please see @Cloud ‘s answer for more info.
Safety
While efficiency is important in aviation, safety is paramount. A go-around may result in time penalties and burn an additional 600 kg of fuel, but it ensures the safety of the flight. The flight may remain profitable despite a go-around and additional 15 mins of flying.
1: For a jet aircraft the controls still have good authority at landing speeds, whereas during training on lighter aircraft the controls feel very sloppy at such speeds. The pilots may instinctively go back to training muscle memory as opposed to the correct technique of holding the landing attitude. Alternately they may just keep pulling back as it is instinctive to reduce rate of descent, though this reduces tail clearance.
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4$\begingroup$ "The flight may remain profitable despite a go-around and additional 15 mins of flying": but since safety is paramount, whether the flight remains profitable or not isn't a factor in the decision. Even if the flight ends up losing money, it will lose less money than would a crash. $\endgroup$– phoogCommented Aug 9 at 8:33
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5$\begingroup$ Yes, if you are driving on the freeway/motorway and miss your exit, you aren’t going to start reversing your car backwards just to get to the exit. The safest thing to do continue to the next exit. Likewise in aviation a hard bounce is a potentially dangerous, unsalvageable situation. $\endgroup$ Commented Aug 9 at 8:55
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$\begingroup$ Additionally the airplane can falsely assess its position as being on the ground when it is actually aloft. $\endgroup$ Commented Aug 10 at 11:11
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1$\begingroup$ Would it be fair to say that unless a runway is extremely long relative to a plane's requirements (e.g. double or more), a pilot who is suitably conscientious about deciding whether to continue a landing that doesn't go perfectly according to plan would generally use enough runway while making that decision that a goaround would be indicated for that reason even if for no other? $\endgroup$– supercatCommented Aug 10 at 18:05
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$\begingroup$ @supercat some situations require a mandatory go around - such as a hard bounce or windshear etc etc. Other situations such as long landing alerts may be ignored and the landing attempt continued if the runway is long enough. Depends on the situation you find yourself in. Also strongly depends on your company’s standard operating procedures (SOPs) $\endgroup$ Commented Aug 10 at 20:27
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Here's a good reason. If you bounce hard enough, the plane flies again. To get it down, some people then push the nose down, which causes another hard landing and another bounce, this is know as "porpoiseing down the runway" and is a quick way to run out of runway and overshoot the threshold.
Profits "should" not be prioritized over safety, hence the go-around.
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2$\begingroup$ For aircraft the size of an a320 series, a seen in the video, the plane will typically sink fast after a bounce rather, the greatest risk being a tail strike. $\endgroup$ Commented Aug 9 at 7:18
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Isn't it a loss of profits for the airline?
It surely costs more than a perfect landing would have, but at the point of deciding to go around, a perfect landing is no longer an option. As others have noted, the go-around is mandated on safety grounds, so the cost/benefit analysis requires looking at the consequences of not going around: the risk of damaging the aircraft, the cost of additional inspections to assess whether such damage has occurred, possible loss of the aircraft altogether, and liability to the airport, passengers, shippers of cargo, adjacent landowners, etc., in the event of damage or injury. The cost of the go-around is justified on these grounds, as are the costs of safety measures generally.
In other words, not going around might result in a far greater loss of profit for the airline.
