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I recently traveled from Stansted, UK to Skavsta, Sweden with Ryanair, and was informed that depending on the weather (it was very foggy), we might end up landing at Arlanda (~150 km from Skavsta) instead.

The pilot later decided to try landing, went down to what felt like 20–50 meters (I could see the airport as clearly as one can see an airport in thick fog...) and suddenly rose sharply and then leveled out, causing some serious roller-coaster-like ~0g feelings.

The pilot then tried a second time and landed without much trouble.

How often does this occur? Was it dangerous? Is it according to standard procedure when approaching an airport in bad weather conditions? What might have caused the pilot to actually land the second time but not the first?

David Richerby
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Mårten
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    I never ever had a single canceled landing attempt, and neither did anyone else at the club I was flying at. Of course, the fact we were flying gliders might have had an influence on it :) – vsz Sep 23 '14 at 18:18
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    It's not really relevant to the question as asked, but still a fun, related fact: whereas in civilian landings, there's a lot of margin for error, in carrier landings, if your tailhook doesn't catch the wire, you could simply fall off the end of the deck. For that reason, all carrier landings are conducted at full or near-full power, so that a failed "catch" results in the pilot simply taking right back off again. I've heard that on the first carrier landing day for new pilots, there is often a betting pool for how many go-arounds there will be. – BMDan Sep 23 '14 at 19:24
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    @BMDan, technically, every carrier landing is flown as a go-around. It's just that some of the go-arounds are aborted when the tailhook catches an arresting wire. – Mark Sep 23 '14 at 23:58
  • Sometimes its not such a dramatic event - I once was in a 747 that had to do a go around as a single runway airport - because there was a rabbit on the field. How do I know this? I saw it scamper away. – Burhan Khalid Sep 24 '14 at 12:07
  • @LightnessRacesinOrbit Thanks for the defense, but I gotta agree with SQB here; Mark nailed it. – BMDan Sep 24 '14 at 14:41
  • @BurhanKhalid Rabbits along runways are quite common. Seeing a rabbit scampering away from a side window in the passenger compartment does not necessarily mean it had been in the path of the aircraft. – Terry Sep 24 '14 at 17:41
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    It was because the pilot announced it as the plane started going up. – Burhan Khalid Sep 24 '14 at 18:13
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    @BurhanKhalid But then, that's how you know it… – Relaxed Sep 25 '14 at 10:53

5 Answers5

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I could see the airport as clearly as one can see an airport in thick fog...

If you saw the runway by looking down from your passenger seat as the airplane passed over the airport on the missed approach, you were looking only through an amount of fog approximately equal to the altitude of the aircraft above the ground. For purposes of discussion, let's say that was 50 meters. The pilot, however, is looking through the front windshield trying to see the runway ahead to position himself for the landing. If he was on a standard 3 degree approach slope, that would mean he is having to look through nearly a kilometer (beware of old man doing math in his head) of fog.

Years ago when I flew for a commuter, I often had to make multiple missed approaches at Pullman, WA, USA in snow storms. My rule was that I would try 3 times before diverting. When we diverted we would often get complaints from passengers about not landing because they could see the airport as we passed over it. I could, too, but only through the cockpit side window, and with featureless snow covered rolling hills, there was no way to position for the landing without losing sight of the airport.

What might have caused the pilot to actually land the second time but not the first?

The thickness of fog or how hard it's snowing or raining is constantly changing. Try again and you may be able to see what you couldn't before. If you can't, maybe try a third time and get lucky. Trying more that that would mean eating into your fuel reserve to get to your alternate, and, just as importantly in my view, pilot fatigue becomes a problem. Plus, you're beginning to seriously blow your schedule.

svick
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Terry
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    ditto. One frustrating night a shallow fog bank forced 2 go-arounds for lack of visibility. Yet flying above it we could clearly see the runway and all the lights. And frankly we tested "landing environment in sight" to its limit when we finally landed. – radarbob Sep 25 '14 at 03:33
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Q: Was it dangerous? Is it according to standard procedure when approaching an airport in bad weather conditions?

If the aircraft did not go below the Decision Height, no, it was not dangerous and it was according to standard procedures.

Decision Height is defined as

DECISION ALTITUDE/DECISION HEIGHT [ICAO Annex 6] - A specified altitude or height (A/H) in the precision approach at which a missed approach must be initiated if the required visual reference to continue the approach has not been established.

[...] decision height (DH) is referenced to the threshold elevation.

The required visual reference means that section of the visual aids or of the approach area which should have been in view for sufficient time for the pilot to have made an assessment of the aircraft position and rate of change of position, in relation to the desired flight path.

and

DECISION HEIGHT- With respect to the operation of aircraft, means the height at which a decision must be made during an ILS, MLS, or PAR instrument approach to either continue the approach or to execute a missed approach. This height is usually 200ft.

This means that when the aircraft arrives at the DH, the Pilot Flying (PF) must have decided whether to land or not. If an abort is initiated, he/she cannot modify the decision (as it would be unsafe)and a new decision has to be made during the new attempt.

If the pilot decided to attempt the landing, but conditions change later during the attempt, the pilot can still decide to abort (as in this case). The decision will be based on the current assestment of remaining available runway, aircraft speed, aircraft attitude and current engine throttle.

Q: What might have caused the pilot to actually land the second time but not the first?

The most likely cause is lack of visibility. In borderline conditions, a plane will normally follow an instrument approach down to decision height. At that height they look up, and if they see the runway clearly they land. If they don't they abort. The first time they didn't see it, and the second time they did.

In the general case, other conditions that might cause a go-around are:

  • lack of preparation – “rushed” approach
  • a late runway or approach procedure change
  • an inadequate approach briefing
  • challenging prevailing wind velocity
  • inappropriate energy management
  • inadequate traffic spacing
  • unfamiliar approach - maybe a straight in non-precision or circling
  • inappropriate aircraft configuration
  • runway surface condition
  • a predicted late touchdown point
  • unexpected runway occupancy after clearance to land
  • degraded aircraft systems status
  • the effect of fatigue
  • the effect of commercial and personal pressure (stress)

As for whether is common or not, I have no statistics at hand, but a go-around is definitely not unheard of. In Richard's answer there is a statistic for a specific airport (Heathrow).

FreeMan
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Federico
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  • The link actually has some statistics: 3% unstabilized, 3% of those are go-arounds, so that's 0.09% go-arounds for that reason. But weather-related go-arounds are not (all) included in that number. – MSalters Sep 23 '14 at 15:31
  • @MSalters I meant the % of approaches resulting in a go-around, irrespective of the reason, weather or not. – Federico Sep 23 '14 at 15:52
  • I think you omitted what is the most likely cause, given the circumstances, which is visibility. – DJClayworth Sep 23 '14 at 17:06
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    The normal procedure for a poor visibility landing is that the plane follows instruments down to the Decision height. At that height they look up from their instruments. If they see the runway clearly they land. If they don't they abort. I would expect that was what happened here. It's not about an inadequate briefing. – DJClayworth Sep 23 '14 at 17:11
  • @DJClayworth oh, totally missed that, thanks. feel free to edit the answer. – Federico Sep 23 '14 at 17:21
  • "Whatever the decision, he/she cannot change it" -- there are videos that show go-arounds initiated after the main gear contacted the runway (e.g. here) -- does that mean that the decision height was nil, or is it actually possible to change the decision in some cases? – hmakholm left over Monica Sep 23 '14 at 18:33
  • @HenningMakholm it means that after DH the pilot proceeded and touched the ground as per decision then proceeded to go-around. Pilots obviously have leeway to ensure the safety of the aircraft, but that directive is to avoid them to second-guess themselves constantly. – Federico Sep 23 '14 at 18:38
  • Just to be precise (or pedantic), it's allowable (and indeed unavoidable) to go below DH on the missed approach. When the decision is made, power is applied, but the airplane will continue to sink some before it transitions to the climb. – Brian Knoblauch Sep 23 '14 at 19:57
  • "..cannot change it..". Agreed. At decision (a.k.a. "minimums") decide. Either continue for landing or go around, you can't do both. As for the practical issues in the answer, certainly in the USAF if we don't have our ahem together by the final approach fix - before minimums on a precision approach - regulations required a go around. – radarbob Sep 25 '14 at 03:23
  • "... no, it was not dangerous and it was according to standard procedures." In fact it can be dangerous to go around after decision height as TERPS bases obstacle clearance on the assumption you are at decision height when initiating go-around (yes, there is a fudge factor for the additional, slight decent). P.S. we're talking IFR criteria here. – radarbob Sep 25 '14 at 03:39
  • @radarbob In fact I wrote if it was not below DH then it was not dangerous. – Federico Sep 25 '14 at 05:40
  • @Federico, yeah, I realize that; I'm just trying to make the point that "minimums" is the point where you know that given a "standard", minimum aircraft climb performance you will clear obstacles through the missed approach. Now we have a reference to define "dangerous". Of course a go-around even after touching down can be quite safe 99.9999% of the time. But if you're near Max GW, engine out, flying into a valley on a foggy night you don't have to bet your life on an uninformed WAG. – radarbob Sep 26 '14 at 03:44
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I don't have any statistics to tell you how common this is, but I can tell you it's absolutely normal. I did it myself two days ago in a small Cessna. Wikipedia says "Go-arounds occur with an average rate of 1–3 per 1000 approaches" but doesn't cite a reference.

The term for what you described is a "go-around": the aircraft cannot land safely for one of several reasons so the pilot decides to increase power, climb higher and go around for a second landing attempt.

A go-around can be required for various reasons, e.g.:

  • The pilot cannot see the runway clearly enough
  • There is another aircraft, a vehicle or some obstruction on the runway
  • ATC instructs the pilot to go around
  • A sudden wind shift makes the aircraft's approach unstable

Based on what you described, it sounds like the aircraft was on an instrument approach, which simply means that the pilot was following a radio or GPS signal to the runway because the fog prevented him from seeing it. The basic idea behind an instrument approach is that you follow the signal down to a pre-defined minimum safe height above ground and at that point if you still can't see the runway and land safely then you have to go around. I guess that your pilot didn't see the runway clearly enough in time and decided to go around, although it could have been for another reason.

The minimum safe height depends on several factors: the aircraft, the equipment it has, the pilot's training and possibly the airline's own policy on approaches. If the weather is so bad that there is little chance of landing then the pilot can try again as he did in your experience or he can divert to a different airport. Again, there are both legal and company policy considerations on when and where to divert.

Pondlife
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How common? Heathrow published (PDF) 0.24% for 2010.

As a passenger I have, just, beaten this statistic with one go-around (at LHR, incoming from Sao Paulo, Brasil) in a total of about 200 lifetime arrivals worldwide.

Farhan
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Richard
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  • Yeah, I've also had exactly one go-around (wake turbulence, at MAN) in, I guess, ~100 landings. But, with the average rate of go-arounds being probably less than the average number of landings people have experienced, most people will have experienced either no go-arounds or an above-average number of them. – David Richerby Sep 24 '14 at 14:19
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    Averages of small integer quantities will do that to you. Similarly, the vast majority of people have an above-average number of legs. – Steve Jessop Sep 24 '14 at 16:00
  • @Steve Jessop Yes, I know that the noise on random quanta is sqrt(n). No statistical significance can be given to my personal experience. I included it for fun. :) – Richard Sep 24 '14 at 16:39
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    As a passenger, I've had one go-around. As a (student) pilot, I've had a lot of them. - lol - On the one where I was a passenger, it was a Southwest flight where we stayed relatively high (~15,000 ft) much longer than normal (presumably due to the thunderstorm that we were flying around at the time,) then basically tried to dive-bomb Tampa International. They couldn't get the speed down quickly enough to stabilize the approach, so they went around. We got a nice ~10-15 minute scenic flying tour of Tampa Bay and still arrived on time. – reirab Sep 24 '14 at 22:20
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Aborting a landing attempt is called a "go around", because the pilots usually choose to turn around and try again.

London Heathrow reported 551 go arounds in 2010, which is less than 2 per day and represented 0.24% of the total arrivals.

The topic of go arounds came to light after the Asiana 214 crash at San Francisco International last year. According to this information based on the first 7 months of 2013, go arounds happened on 1.31% of approaches for foreign pilots, but 0.28% for domestic pilots (which is close to the figures reported at Heathrow).

Information from CASA in Australia says there are over 800 per year there, but no accompanying number of arrivals is provided.

Using separate statistics, for domestic and international traffic, there are 702321 domestic flights and 162207 international flights in 2013. If only half of the international flights were landing (the other half departing), this represents 783425 landings. Assuming 850 go arounds per year, that is 0.11% of arrivals in Australia. Being averaged over the whole country could account for the lower percentage. Some causes for go arounds such as conflicting traffic would be less common at less busy airports.

According to a consultant on this story, go arounds occur in 0.20% to 0.33% of landings, which matches the other statistics.

So the numbers show that go arounds are not that common, but they do happen regularly and exactly how often this happens depends on many factors. It is much safer to stop a landing and try again than to continue with an approach that could compromise the safety of the flight.

If the pilots have not established the proper altitude and speed in the approach, they should automatically go around rather than attempt to land. They are also required to go around if they cannot see the runway for visual reference by a certain point. If they do not go around, there may be an investigation, because this can lead to a landing accident, which is far more dangerous and costly than just going around.

By going around, the pilots are hoping that the weather conditions will change enough for the next approach to be safely possible. Low visibility weather like fog can easily change in a short time, so if the conditions are only slightly worse than what is allowed, it may clear up just enough to allow a safe landing.

fooot
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    Interesting statistics. Also, Asiana 214 is a good example of why you should abort the approach if you haven't stabilized your approach by the time you reach minimums. Of course, it's also a good example of why you should closely monitor your airspeed on final. – reirab Sep 25 '14 at 13:45