Aug

3

Recently I did a search of Daily Speculations for "Ever changing cycles" and waded through the gold mine of thoughts that it yielded. I was caught up by the Chair's "Knowing Your Limits" from May of 2007.

Intrument PanelWhen flying airplanes there are a plethora of limits that must be obeyed. Especially speed limits. Many, many speed limits. During the take off roll of a commercial airliner, the pilot not flying is responsible for watching certain things but most importantly the airspeed indicator. He will make audible calls to the pilot flying. If the aircraft has an engine failure or some other failure that requires an aborted take off, this must occur prior to reaching a speed called "V1". At speeds prior to V1 the aircraft is still capable of stopping safely without going off the end of the runway. V1 is calculated for each runway and can change due to temperature and humidity. If V1 is exceeded, the aircraft will continue accelerating to V2 (minimum safe take off speed) and to Vr (rotate, or lift the nose) even if an engine is lost prior to V2 (in a multi-engine aircraft of course). Once an aircraft is airborne, pilots will want to maintain either Vx (best angle of climb, used for obstacle clearance) or Vy (best rate of climb) for the climb out, then at certain speeds flaps and slats can be retracted. The list goes on. One of the first speeds that all pilots learn is the stall speed for the aircraft they are flying, or Vs. At speeds below Vs the airflow over the wings will separate from the wing causing a loss of lift or stall. Most airlines prohibit operation of an aircraft at speeds below 15% above the stall speed. Pilots are not permitted to exceed 250 KIAS (knots indicated airspeed) below an altitude of 10,000 feet.

Controllers routinely assign speeds to aircraft to maintain safe spacing. It is common to assign jets speeds ranging from 250 to 320 knots. Once aircraft reach altitudes of about 26,000 feet they will typically stop using indicated airspeeds to control their speeds but switch to Mach number, a ratio of true airspeed to the speed of sound . Aircraft must use a Mach meter at higher altitudes because they must be sure not to exceed M mo or maximum operating mach number or the critical Mach number for the aircraft, this is a speed at which, although the aircraft has not exceeded the speed of sound, the airflow over certain parts of the wing may do so locally causing a shock wave to form and a dramatic increase in drag and possible disturbances to control surfaces (ailerons, rudders etc.) ability to perform.

As an aircraft approaches its service ceiling it is no longer able to climb at a rate that will produce gains in operating efficiency.

Aircraft limits are hard and fast based on the laws of physics. Limits in speculation are much more subjective and one has to develop a feel for ones own limitations and expand beyond them incrementally so as not to do too much damage in the process.

Speculators are subjected to a degradation in performance if certain of their limits are exceeded. I can clearly recall making a trade in which I exceeded my personal size limit and the feeling of utter incapacitation when it went against me. Other limits can be number of trades on at one time or number of markets watched. What limits have you discovered that hamper your performance?

Vin Humbert elaborates:

A limit that comes to mind where you feel that sense of hopelessness that apparently pilots feel when the plane is not under their control anymore comes when you exceed your margin carrying capability. Or worse yet, when the marks on your positions have no relation to underlying related moves but are manipulated against you to force you out of a position. This is guaranteed to happen when there is inadequate liquidity in your market of choice relative to your position size. Wisdom comes too late in many cases.

Chris Tucker continues:

Obstacle clearance speeds are dynamic, that is to say that they vary with windspeed and direction and with density altitude so must be calculated based on these things for the runway in question. Take a peak at V speeds and Airspeed indicator  for interesting reading.

Chris Cooper writes:

I have recently started learning to fly helicopters, and there are more critical speeds not listed in the references given. For example, every helicopter pilot wants to know the best autorotation speed, which is the speed you shoot for when your engine fails. With the right speed you can keep the main rotor turning [and the helicopter slowly descending], but if you mess that one up [so the rotor speed falls below a critical value], you fall out of the sky.


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