15

The spoilers on the Airbus A300 have large gaps at the bottom:

A300 wing
(A300-600R, modified from Wikimedia Commons, original picture by Tennen-Gas, CC BY-SA 3.0)

I have never seen any other aircraft with such gaps in the spoilers. Airbus also got rid of them on the A310:

A310 wing
(A310-322, ETH-Bibliothek Zürich, picture by Swissair, CC BY-SA 4.0)

Since the point of spoilers is to disrupt airflow on the top of the wing to reduce lift, it seems counter-productive to include such gaps. So what is their purpose?

Bianfable
  • 55,697
  • 8
  • 195
  • 257
  • 1
    I cannot answer with scientific accuracy, but the gaps do not diminish the efficiency of the spoilers in a significant manner, but relative to their size the pitching moment and actuation force required are smaller compared to a "solid" version. – Jpe61 May 31 '21 at 09:49
  • What do dive brakes have to do with it???? – John K May 31 '21 at 23:38

1 Answers1

10

Literature on the A300's spoilers is lacking, so is the flight manual's description. But based on publicly available information, there is a very strong candidate for a reason.

The A310's wing is very different from the A300's. Of the relevant differences, the A300's wing is:

  1. Thinner[1] (you can also visually tell: wing thickness under the deployed spoilers and spoiler thickness)
  2. Outboard section having double-slotted flaps (not on the later model -600R shown in the question)[2]

enter image description here
Three different A300/A310 flaps,[2] and A300 v A310 wing thickness[1]

Both of which when combined would lead to a spoiler mechanism packaging difficulty, which leads to smaller spoiler actuators. The A300's spoiler with a gap would lessen the low pressure behind the spoiler, making it easier to deploy and hold.

In fact, the inboard spoilers where the wing is thick, the spoilers are normal:

enter image description here
— Lufthansa Airbus A300 Landing Berlin Tegel (YouTube)

Another airliner with such a gap is the Caravelle VI-R. The gap is referred to as a breather slot:

[Spoilers] require holding open as the airflow tends to blow them closed. Some [spoilers] feature breather slots, e.g. the ones of the Airbus A300 and Sud Aviation Caravelle.[3]

1: Airbus FAST magazine #5 (PDF)
2: Aerodynamic Design of Airbus High-lift Wings in a Multidisciplinary Environment (PDF)
3: Alternative Air Brake Concepts for Transport Aircraft Steep Approach (PDF)

  • Beautiful answer, any idea why the A321 breaks with the flap-trend so obviously? – ROIMaison Jun 02 '21 at 11:53
  • 1
    Thanks @ROIMaison / See p. 7 of the second ref. In short, Airbus favors high-lift wings w/ simple flaps, but since the A321 came after the 320 (a stretched variant), to avoid redesigning the landing gear and to achieve similar performance the flaps were made double-slotted. Not in the ref.: a similar thing happened w/ the 350 stretch (the -1000) where they had to redesign the aft part of the wing. Boeing on the other hand favors high-lift flaps, which doesn't require changing when stretching models. See this post for more. –  Jun 03 '21 at 02:20
  • 1
    Nice one. I even found a photo of the Caravelle with spoilers deployed. – TomMcW Jun 04 '21 at 17:49