The Nine Deadly Sins Presented by KVGT FAASTeam Sign Log In Sheet for Wings Credit Stephen Ruks ATP, CFII

The Nine Deadly Sins References Pilots Handbook of Aeronautical Knowledge Ch. 7 & 10 Your AFM or POH AC 00-6A Aviation Wx AC 61-84B Role of Preflight Preparation FAA-P-8740-2 Density Altitude Brochure FAA Aviation News May-June 2004

The Nine Deadly Sins What is one of the best things you can do to avoid being a sinner? Enroll in the WINGS program! FAA Safety - FAASTeam and Wings

The Nine Deadly Sins Introduction Misunderstandings or lack of knowledge about our atmosphere and how it affects aircraft performance is one of the leading causes of fatal aviation accidents. This seminar will remind you of some of the things you already know and maybe show you a few things you didn’t know.

The Nine Deadly Sins Altitude Types How many altitude definitions are there? Indicated altitude True altitude Absolute altitude Pressure altitude Density altitude Read on your altimeter Height above MSL Height above ground level Indicated altitude set at 29.92 PA corrected for non-standard temperature and humidity 1. Indicated altitude—read directly from the altimeter (uncorrected) when it is set to the current altimeter setting. 2. True altitude—the vertical distance of the aircraft above sea level—the actual altitude. It is often expressed as feet above mean sea level (MSL). Airport, terrain, 7-7 and obstacle elevations on aeronautical charts are true altitudes. 3. Absolute altitude—the vertical distance of an aircraft above the terrain, or above ground level (AGL). 4. Pressure altitude—the altitude indicated when the altimeter setting window (barometric scale) is adjusted to 29.92 "Hg. This is the altitude above the standard datum plane, which is a theoretical plane where air pressure (corrected to 15 °C) equals 29.92" Hg. Pressure altitude is used to compute density altitude, true altitude, true airspeed (TAS), and other performance data. 5. Density altitude—pressure altitude corrected for variations from standard temperature. When conditions are standard, pressure altitude and density altitude are the same. If the temperature is above standard, the density altitude is higher than pressure altitude. If the temperature is below standard, the density altitude is lower than pressure altitude. This is an important altitude because it is directly related to the aircraft’s performance.

The Nine Deadly Sins Pressure How do we describe atmospheric pressure, what is it, and how does it affect us? More importantly, how does it affect our airplanes?

The Nine Deadly Sins Pressure What causes pressure variations? Altitude Pressure decreases approximately one inch of mercury per 1000 feet increase in altitude. Temperature Temperature is the biggest factor affecting density altitude. Temperature changes ≈ 2ºC/1000ft

The Nine Deadly Sins Pressure Gradient Given the same change in pressure, the rate of change of pressure is greater in cold air than in warm air.

The Nine Deadly Sins Effect of non-standard temperature

The Nine Deadly Sins Typical GA Pitot System

The Nine Deadly Sins Typical Altimeter

The Nine Deadly Sins Altimeter Setting Standard Atmosphere: 29.92 inHg or 1013.25 hPa (or mb) At sea level @ 59º F (or 15º C) One inch of mercury = 1000 feet One hectoPascal = 100 millibars 1 inHg = 33.86 hPa

DA= Tsl γ 1 − 𝑃/𝑃𝑠𝑙 𝑇/𝑇𝑠𝑙 𝜞𝑹 𝒈𝑴−𝜞𝑹 The Nine Deadly Sins Density Altitude How do we calculate Density Altitude? DA= Tsl γ 1 − 𝑃/𝑃𝑠𝑙 𝑇/𝑇𝑠𝑙 𝜞𝑹 𝒈𝑴−𝜞𝑹

The Nine Deadly Sins Density Altitude Three important factors contribute to high density altitude Altitude Temperature Humidity Reduced air density equates to decreased performance

The Nine Deadly Sins Density Altitude Warmer air will hold more water vapor than cooler air which affects engine performance more than aerodynamic performance. With high humidity, expect longer take-off rolls and lower climb rates. Add 10% to take-off distance.

The Nine Deadly Sins The Nine Deadly Sins (and their unforgiveness) Using sea level VSPEEDS Using gross weight VSPEEDS Ignoring effect on TAS Ignoring effects in mountainous terrain Ignoring effects on landing speed and distance Ignoring climb gradient Ignoring runway environment Using incorrect flap settings Combining soft-field and obstacle techniques

The Nine Deadly Sins 1. Using Sea Level VSPEEDS Best Climb Chart

The Nine Deadly Sins 1. Using Sea Level VSPEEDS High density altitude affects take-off & landing distance Always follow manufacturer’s recommendation.

The Nine Deadly Sins 2. Using Gross Weight VSPEEDS 𝑉𝑦𝑐𝑢𝑟𝑟𝑒𝑛𝑡 =𝑉𝑦𝐺1 2 𝑊𝑐𝑢𝑟𝑟𝑒𝑛𝑡 𝑊𝑔𝑟𝑜𝑠𝑠 Climb performance decreases with increase in gross weight

The Nine Deadly Sins 3. Ignoring Effect on TAS IAS = 150 PA = 8000 Vy Temp = 95ºF TAS = 180 DA = 12,000 Vy TAS Vx TAS

The Nine Deadly Sins 3. Ignoring Effect on TAS IAS = 150 PA = 8000 Temp = 95ºF TAS = 180 DA = 12,000 Turn diameters increase. Bank angle = 23=SRT ((v² / (11.26 x Tan Φ)) x 2) / 6076 ((150² / (11.26 x 0.4245)) x 2 ) / 6076 = 1.55NM @ 180 TAS = 2.23NM Turn diameter increased by 50%

The Nine Deadly Sins 4. Ignoring Effects In Mountainous Terrain TAS increase causes turn diameter to increase

The Nine Deadly Sins 4. L - D Chart Bank Angle Load Factor %Increase in Induced Drag 0 1 0 15 1.036 7.2 30 1.154 33.3 45 1.414 100 60 2 300 Stall speed (VS1) increases a whopping 41%

The Nine Deadly Sins 5. Ignoring Effects on Landing Speed and Distance PA=4000’, 25ºC, No wind – 1200ft PA=6000’, 38ºC, 10kt Tail – 2200ft PA=6000’, 38ºC, 10kt Tail – 3400ft w/ obstacle

The Nine Deadly Sins 6. Ignoring Landing Distance 8000’ elevation, 2500’ long, downslope, tailwind, cliff

The Nine Deadly Sins 6. Ignoring Climb Gradient Climb gradients are in Feet/Mile not Feet/Minute (as read on VSI) Use TAS (or GS) not IAS to calculate climb gradient

The Nine Deadly Sins 6. Ignoring Climb Gradient

The Nine Deadly Sins 6. Ignoring Climb Gradient

The Nine Deadly Sins 7. Ignoring Runway Environment A36 Takeoff OAT = 97F, Field Elev =1293’ Altimeter 29.89” Density Altitude = 4125’, Rwy 31 4000’ paved 1996 A36, Turbonormalized IO 550, GTOW = 4095, CG = 86.15”

The Nine Deadly Sins 8. Using Incorrect Flap Settings In the A36 incident, use of flaps may have made the situation even worse! Use of the recommended flap setting works just fine when operating at near sea level altitudes but with non-turbocharged engines, there comes a density altitude above which the use of takeoff flaps actually increases ground roll.

The Nine Deadly Sins 9. Combining Soft-Field & Obstacle Techniques Normally flaps only used on soft field takeoff but when used for obstacle clearance, the increase in drag drastically hinders climb performance. Always follow manufacturer’s recommendation.

The Nine Deadly Sins Summary Beware, better yet, be knowledgeable, of the Nine Deadly Sins of Density Altitude Remember the effect of DA on TAS and the TAS effect on airplane performance Engine performance degrades with altitude and humidity! Always use POH or AFM recommendations

The Nine Deadly Sins Any Questions?

The Nine Deadly Sins That’s all folks!

Door Prize! The Nine Deadly Sins Remember to sign the Log-In Sheet for credit. Stephen Ruks ATP, CFII, BPPP 702.533.1978 beechflyer@icloud.com

The Nine Deadly Sins Remember to sign the Log-In Sheet for credit.

The Nine Deadly Sins The end . . . . . .