David Irwin looks at how runway alternation following the 3rd Runway will impact Putney

Due to prevailing westerly winds planes approaching Heathrow overfly west London. There are two runways. For half the day planes land on one and at 3.00pm they switch to the other. This is called runway alternation.

When the wind is from the east the direction of approach is reversed. Planes arrive from the west and do not overfly London. Unfortunately, easterly winds are not common and only account for approximately 25% of our weather.

There are 480,000 flights per year, of which approximately 360,000 (75%) arrive over London. Of these, half (180,000) land on the southern runway and overfly Putney, a frequency of about one every 90 seconds. When planes land on the northern runway they overfly Hammersmith and Fulham.

Heathrow intends to build a third runway and increase the number of flights by 50% to 720,000 flights per year. This will entail a different operational mode involving an important change to the existing runway alternation.

The four figures show the three runways and the manner in which they will be used when the wind is from the west. For easterly winds the method is similar except that planes approach from the west.

Two of the runways will only be used for planes to land. One of the runways will be mixed mode which means that planes will both land and take off, in the same direction.

Four modes of operation are proposed. Of these only mode 1 ensures that no planes overfly Putney.

The plan is to vary modes over a 4 day period according to the schedule shown below. For Putney there will be only two half days within four full days when no planes overfly residents.
Put another way, when winds are from the west planes will pass over Putney for 75% of the time. Compared with the present arrangement, where planes overfly for half the time, this represents a significant increase in noise.

Moreover, the increase in the total number of flights will also have an impact. About 540,000 flights will arrive over London. 75% of these will land over Putney. This amounts to as many as 400,000, more than double than at present.





If you find this unacceptable you should immediately voice your concern before the Heathrow consultation closes on the 13th of September by :
e-mailing feedback@heathrowconsultation.com
or by writing to FREEPOST LHR AIRPORT EXPANSION CONSULTATION

David Irwin

September 12, 2019