The principle: Start from the junction
An intersection take-off refers to take-off from a cross-connection of the runway, i.e. not from the beginning of the runway, but from an intersection - typically a taxiway that runs at right angles to the runway. This saves taxiing time and can make air traffic more efficient, especially at large commercial airports. However, the shorter route to the take-off position also means a reduced take-off distance.
Until recently, pilots of small aircraft in Germany and many other countries had to give their explicit consent if the tower offered them a take-off from an intersection. This procedure has now been simplified: for aircraft under 2000 kg MTOM (Maximum Take-Off Mass), the controller may assign the intersection take-off directly - and the take-off is now authorised. unless the pilot explicitly requests the full runway lengthwhereupon the tower may not refuse.
Safety first: Why more runway never hurts
In aviation, there is a common expression: "The most useless runway is the one behind you." This means that unused runway length is not available if something goes wrong during take-off. In fact, a longer runway significantly increases the room for manoeuvre:
- More time and distance in the event of unexpected incidents such as loss of power
- Safe decision via an aborted start (70/50 rule)
- Higher top speed before take-offwhich can improve the climbing performance
Particularly with short tracks, it is risky not to utilise the entire length. The classic "backtrack" - rolling back to the end of the lane - costs time, but can be decisive in an emergency.
Efficiency for large spaces: Intersection take-offs in scheduled transport
At large airports such as Paris Charles de Gaulle, Frankfurt or Munich, intersection take-offs are an integral part of the process planning. The tower controllers use several taxiway junctions along the runway to ensure Fine-grained clocking during take-off. This means that aircraft with different take-off distances, climb profiles and speeds can be better staggered.
This is particularly relevant in mixed traffic: spaces often have to be created between fast IFR airliners and slower VFR aircraft such as motorised gliders or training aircraft. Intersection take-offs allow small aircraft to merge into the traffic flow in a targeted manner.
Practical advantages for general aviation
Intersection take-off offers practical advantages for pilots of single-engine or light twin-engine aircraft:
- Time saving when rolling
- Avoidance of jetblast zones behind airliners
- Possibility to utilise small start gaps
- Lower risk of getting caught in queues
However, the opposite can also be the case: If you insist on the full runway, you may have to wait until all larger aircraft have been processed during busy periods - and lose valuable time. In extreme cases, this can mean that a destination can no longer be reached before sunset or that the destination aerodrome is closed.
What does the technology say?
Aircraft have clearly defined take-off distances in the operating manuals (AFM/POH) for various conditions. Intersection take-offs shorten these reserves. Even if 2,000 metres remain, the decisive factor is whether the aircraft can take off safely even at maximum take-off weight, high density altitude and crosswinds. Even more important is the question of Stop distance in case of aborted start: At low altitude, there is often insufficient room for a safe landing, even if the runway appears long.
The so-called "RTO decision" (rejected take-off) must also be made at an early stage - for example, if 70 per cent of the take-off speed has not yet been reached at 50 per cent of the take-off distance.
Risks: Runway incursions and misunderstandings
Intersection take-offs also harbour a certain risk for Runway Incursions - unauthorised use of an active runway. Misunderstandings can occur, particularly at larger airports with parallel or intersecting taxiways. Historical accidents such as the one at Charles de Gaulle Airport in 2000 show that language barriers, radio misunderstandings and distractions can have tragic consequences.
That is why it is important:
- Radio discipline and active listening
- Correct feedback of approvals
- Eye contact with approaching machines
- Awareness of the lines of sight at intersections
Wake vortices - the invisible risk
Especially when there is no wind or little wind Wake vortices a factor to be taken seriously. If an airliner has just taken off, its turbulence can persist for several minutes - and jeopardise small aircraft. That is why a Minimum distance of 2-3 minutes advisable, even if the tower has already issued a clearance. Pilots should actively request this and, for example, announce it during the radio handover ("request 3 minutes behind heavy departure").
Conclusion: Intersection take-off - a decision with responsibility
Intersection take-offs are an efficient and sensible instrument of modern aviation, provided that they are be used consciously and responsibly. They offer more flexibility in flight operations and relieve the traffic flow - but can quickly become safety-critical if they are neglected. The following applies to pilots: precise knowledge of take-off performance data, a keen eye on the weather, traffic and infrastructure and a realistic assessment of their own capabilities are essential.
Because as useful as every minute of time saved may be - none is worth jeopardising safety.
Source references:
Aviation magazine