7
$\begingroup$

Clearly the angle at which planes take off and climb depends on lots of things (mountains, residential area, aircraft type, wind) but when watching planes take off after another from the same runway, I have the impression that similar aircraft climb at different angles right after another.

So I'm wondering it this is a measure to increase the distance between two planes quickly after they leave the airport? Such that every other aircraft is asked to leave flat'ish (within what the plane and regulations allow) and others more steeply?

The question occurred to me at GVA (single commercial runway).

This is about the initial climb angle, not their course heading.

$\endgroup$
  • $\begingroup$ I mean the angle that the planes climb at for say the first km of flight $\endgroup$ – pseyfert Aug 18 '17 at 22:32
  • 5
    $\begingroup$ I have proposed an edit to try to clarify that the intent of the question is the climb angle, not heading. This question is now on the hot network questions list, making a clear and unambiguous title all the more important. $\endgroup$ – a CVn Aug 19 '17 at 11:00
10
$\begingroup$

There can be many reasons. Flights taking off one after another:

  • have different destinations
  • have different weight and balance
  • have difference in wings and wingtips
  • have pilots with difference in skills
  • got different takeoff directions by ATC
  • are trying to avoid wake turbulence

Off all the reasons I mentioned above, perhaps wake turbulence might be playing more role about difference in takeoff angle. There are a ton of questions about wake turbulence, which is worth a read.

$\endgroup$
  • 2
    $\begingroup$ Different departure headings is not a valid wake turbulence separation. We need x number of minutes between departures for wake turbulence, regardless of direction of flight. $\endgroup$ – J. Hougaard Aug 19 '17 at 4:54
4
$\begingroup$

No, planes are not assigned a specific climb angle by the tower upon takeoff - the tower will not instruct an aircraft to "climb at FPA 4 degrees" or "climb at 1200 feet/min". Separation is achieved primarily by lateral distance.

If there is a risk of collision (e.g. an aircraft has just taken off, and the landing aircraft executes a go-around), ATC will issue a different heading to one of them.

The initial climb from the runway is hand flown by the pilot; even if conditions are the same, different pilots might have climbed the aircraft at a different angle. Besides, there are quite a few factors which will influence the initial climb you observed:

  • A heavier aircraft will have a higher Vr, which will delay rotation. An aircraft heading to a farther destination will carry more fuel and be heavier, even compared to another aircraft of the same type.
  • If the aircraft is empty (e.g. positioning flight), the pilots can probably climb faster.
  • If the fuselage is long (e.g. 777-300) and the pilot pitch up too much, it will have tail strike.
  • Company SOP may require the pilot to "pitch up to X degrees" for passenger comfort.
$\endgroup$
4
$\begingroup$

Referring to the takeoff pitch angle differences, they are often due to aircraft characteristics or situational things, like potential wake turbulence, or known obstacles. Planes have different speeds for best climb, and that will result in different take off angles. consider an F-18 putting out full afterburners on takeoff. That pilot could go straight up, no problem. At my flight school on the other hand, someone was training in a home-built LSA (I don't remember the type) that I swear had a max fpm climb rate in the TENS. (joking, somewhat). That little plane had to do a LONG and SLOW climb. Anytime in the pattern behind him was laughably interesting, having to extend the pattern in all sorts of ways. That was fun for a newbie trying to learn how to land in the first place.

Aside from that, departures vary for safety and often convenience, keeping planes out of trees, wake turbulence, and other planes. Planes with short takeoff rolls can usually get above obstacles (50') or wake turbulence effects before most of the runway is taken up, allowing for a shallow climb. Other planes might require more runway, leaving a steeper climb required to clear obstacles.

$\endgroup$
  • 1
    $\begingroup$ yes, the initial departure or approach vector is decided at least in part by the performance of the aircraft to have it intercept the first waypoint of the SID/STAR at a decent angle. $\endgroup$ – jwenting Aug 19 '17 at 7:46
  • $\begingroup$ OP clarified in comments they mean vertical climb angle, not heading. $\endgroup$ – Notts90 Aug 19 '17 at 8:40
  • $\begingroup$ Fixed it, thanks $\endgroup$ – ryanrr Aug 24 '17 at 3:18
1
$\begingroup$

A climb rate/angle assignment will not be assigned, altitude only. The standard climb rate is 200 ft/nm unless otherwise published, but ATC won't verbalize the published climb rate unless queried. The closest thing to your question would be the assignment of a departure procedure. DP's have a required climb gradient based on the departure runway to ensure obstacle separation or satisfy noise abatement procedures.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.