ElpinDAB From United States of America, joined Apr 2005, 489 posts, RR: 4 Posted (1 year 11 months 2 weeks 6 days 21 hours ago) and read 3425 times:
This is a broad topic because it varies so much depending upon aircraft type and utilization. Asking about fleet utilization per route could be very complicated, especially for shorter routes, but I'm trying to get a feel for how many aircraft an airline would need to open routes of varying distance and frequencies from multiple airports.
Assume average fleet utilization with minimum "downtime", scheduled inspections, spares, etc.
Are there any general guidelines to follow? I'm sure it would be far easier to determine if one had knowledge from starting an airline and gradually growing larger, but for larger airlines, it seems that for somebody unfamiliar with these practices, it's a daunting question. I have read on these forums that about 3 aircraft are necessary for a reliable ultra-long haul route such as EWR-SIN or ATL-JNB. Those are obviously extreme examples, and easier to determine. How would these look for smaller segment lengths, such as 5,000nm, 4,000nm, 3000nm, 2000nm, etc...down to regional networks where aircraft are generally never more than a couple hundred miles from a hub or maintenance base?
roseflyer From United States of America, joined Feb 2004, 10390 posts, RR: 52
Reply 1, posted (1 year 11 months 2 weeks 6 days 20 hours ago) and read 3390 times:
The easiest way to generate your calculation is to use the average fleet utilization in flight hours per day and divide the block time by that. Average utilization for a 777 including maintenance downtime is about 10-11 hours per day. Lets assume ATL-JNB is blocked at 15 hours each way. That means 30 hours divided by 10 hours which means 3 planes.
The math isn't always that easy. For example with a short turn, less than 3 planes are needed. However, you have to factor in maintenance and the consider that the same 777 may have an 8 hour ground time between flights on its next route due to scheduling. Narrow body airplanes tend to have fewer hours per day than wife bodies because of more ground handling associated with more flights, and also because most are on the ground overnight.
A normal airline has its fleet on a given rotation between A checks. A checks may be every 60 days. The airlines will also schedule 3 - 6 extended ground time blocks (6-10 hours) at maintenance bases to clear any existing problems and keep the fleet healthy to protect from cascading maintenance delays.
Airlines always have a limited number of spare airplanes. They need to cover out of service airplanes for mechanical reason or cover charters, etc. typically scheduled maintenance is already built in the schedule so those are not out of service planes. The spare count varies on any given day and especially seasonally and weekends. It is easy to add a winter turn, but some schedule tends to be tight. Most routes do not exactly equal one plane, so a given route depends on the slack in the fleet. Airlines typically only have about 5-10% spare count.
[Edited 2013-07-18 20:37:04]
If you have never designed an airplane part before, let the real designers do the work!