The chartered plane for the Utah Jazz’s basketball team apparently hit a flock of birds during takeoff and was forced to make an emergency landing yesterday. They were taking off out of Salt Lake International when it happened.
It probably isn’t a big surprise to most that takeoff and landing are the most dangerous periods of just about any flight. They are labeled “critical phases of flight” for that reason. Some military aircraft have additional critical phases like aerial refueling and close air support, but each commercial flight should only have to be exciting twice.
Why Takeoff Is Huge Deal
What is not generally known, are the multitudes of speeds that are important to a pilot taking off in a heavy plane. During take off roll it is important to make sure that both the pilot and copilot’s airspeed readings are accurate, otherwise you don’t know what to trust. So that is typically checked early in the roll. Very soon after that approaches what are called “decision” speeds. These are calculated in advance of takeoff, usually by computer (but can be hand calculated) and displayed in the cockpit for the pilots.
Most of them are based on how much control the aircraft’s rudder will provide based on the loss of an engine. It is assumed to be be most critical engine, which is the upwind (and for 4 engine aircraft, the outboard) engine. This is because if there is any crosswind, the aircraft will already have a tendency to weathervane in that direction. With that engine lost, it will want to turn that way even more.
The faster you go, the more air across the rudder, the more control the pilot has. So more speed, which means more control, is better. But, in accelerating towards getting that control, the airplane is leaving runway behind it.
Decisions Decisions
So there is a point during takeoff, where a very interesting thing happens, unknown to everyone but the pilots. It is the decision speed. I have always heard it announced as V1. It is at this point that the plane is going fast enough to maintain control on the runway in the event of losing the upwind outboard engine. It is not going fast enough, however, to achieve safe flight. The speed at which you transition to a take off attitude is called “rotate,” or the technical nomenclature, Vr. The weight of the aircraft, outside air pressure, and performance of the engines at a certain temperature, determine how big the window between V1 and Vr is. Based on the afore mentioned factors of temp, pressure, and weight, those speeds can be simultaneous, or there can be several very long seconds (and thousands of feet of runway) in between.
If something happens in that window, the pilot is has to put absolute trust in the numbers computed before takeoff. Because those numbers are based on the assumption that there is an engine loss, if it actually happens, there is really not much danger. The pilots train for it all of the time, and it is very rare besides. It is only when more than one engine is lost that you are in uncharted territory.
What About Those Numbers In Practice?
I was in that situation once a few years ago during takeoff from Patuxent Naval Air Station in Maryland. One peculiarity there is that there is a hump in runway 06 where it crosses another runway. Birds can be just on the other side of the bump and unseen to the airplane taking off. There was a pack of sea gulls, and at least one pelican, hidden there just after I had passed V1. So I kept barreling down the runway even after the birds had seen me and started to depart the area. The tower told me that they recovered at least 17 seagulls afterwards. They would never find the pelican because it went straight down the core of one of my turbofan engines. I knew it because we smelled old nasty fish coming out of the bleed air for at least an hour afterwards.
We didn’t lose the engine immediately, but we had to pull it back while we looked at it to make sure it would perform for the planned flight. It turned out that it was fine, and we continued with a shortened version of the mission, always staying in range of an emergency airfield.
For the Pilots, Having All Engines is a Luxury
Even though we didn’t lose the engine on that flight, I have been the pilot on at least one other that had severe malfunctions during takeoff, and the computed data was completely reliable. It is just interesting that the pilots train to the standard that assumes making it airborne with all engines is a luxury, while the reality is that it rarely has to be put into practice. That is a huge win for modern engineering and our training standards.