Lecture #1 Today’s lecture

• Pitot-static systems ASE 167M Lecture One • Bernoulli’s equation • definitions • Instruments Systems • Flight control systems Flight 1 Briefing • Flight 1 briefing

Revised by Greg Holt

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Lecture #1 Lecture #1 Pitot-Static Systems Pitot-Static Systems (2)

• Essential requirements in the measurement of a/c performance are: (1) state of atmosphere and (2) relative motion between the a/c and the air mass ⇒ air data systems • Of the primary (, airspeed, VVI, , turn coordinator), the first three use the Pitot-static system • The Pitot-static systems, drive instruments (movement of a pointer mechanically) that use difference between static and total pressure, or just (independent of electrical power supply) • System includes a for measuring impact (ram) pressure, and static ports for measuring barometric static pressure.

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• Total pressure at a given point is that which would exist if • : Solve (1) for V: the flow were slowed down isentropically to zero. ()− = 2 PT P Vtrue ⇒ Function of 2 variables • Assumptions? ρ V1,P1 Flow Pitot Tube – Isentropic V2=0 ρ = ρ (Sea LevelStandard Atmosphere) – Incompressible P2Static Port –Keep sl – P and ρ are corrected for at flight condition P P T • : • Derived from Newton’s 2nd Law (F = ma) – Speed read on a perfect (i.e. no instrument error PP21−=1 ρ V2 2 1 and true static pressure) 1 ρ – Corrections may be particular to a/c and instruments P+== V2 P const. along streamline () 1 2 T – Take into account position errors =+∆+∆ Static Dynamic Total VVcalibrated indicated VV posit.. inst Pressure Pressure Pressure 2/2/2004 ASE167M Lecture 1 5 2/2/2004 ASE167M Lecture 1 6

Lecture #1 Lecture #1 Airspeed Definitions (2) Airspeed Definitions (3)

• white arc γ −1    • 2γ p pp− γ ⇒V =+− 110  true γρ   – operating range – Corrected for compressibility effects −1 p  γγ  – stall speed (with full flaps + landing (1.4)ratio of specific heats⇒ = for air – Corrected for altitude/density changes gear – landing configuration) to – For incompressible flow we use max. flap operating speed 2()PP− ρ ρ qV==11ρρ2 VV2 ⇒ ==T V • green arc 22sl equiv calρρ true slsl – normal operating range = – stall speed (power-off in clean – We will assume: VVequiv cal configuration) to caution range • yellow arc • – caution range – As measured by airspeed indicator •red line – We will assume: = – never exceed speed Vindicated Vtrue

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• Measures the weight of the air above the A/C ⇒ fly at a constant pressure • Rate of static pressure level change is measured to give −β Rg/ 0  Tp0 an indication of rate of H =− 1 β p 00  altitude change. • Pressure typically decreases, in the lower atmosphere, by a known amount with altitude. • System exhibits a 4-8 second (standard lapse rate) delay before steady state ≈ - 1.00”Hg/1000 ft reading is accurate.

• Static pressure readings are compared • Shows Trend (immediate to a table of pressures to calculate indication) and rate altitude (stabilized) of climb

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Lecture #1 Lecture #1 Example Problem Example Solution (1)

• Altimeter and airspeed indicator read 8000 ft. • Trueρ Airspeed and 120 mph, respectively. Assume that all instruments are perfect. ρ = slug SL 0.00237 3 • A pitot-static tube measures the dynamic ft pressure. = slug 8000 ft 0.00186 3 – What is the true airspeed? ft slug • Assume the a/c flies at the same altitude and ρ 0.00237 ft 3 enters an area of lower pressure. V = V SL =120mph true cal ρ slug – What happens to the altimeter reading? 0.00186 ft 3 – What happens to the airspeed indicator reading? V =135.4mph – What happens to the VVI reading? true

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• (altitude) As the altitude increases, static • , , and turn & pressure decreases. Therefore, the altimeter will indicator or turn coordinator. show an increase. • These devices exploit two properties: (1) rigidity • (airspeed) Assuming constant density, there will be no change in the airspeed indication as the and (2) precession which are based upon the dynamic pressure measured by the pitot-static conservation of angular momentum. tube will not change. – Rigidity is the property which resists any force • (VVI) The static pressure will appear to have tending to change the plane of rotation of the rotor. decreased with time; therefore, the VVI will show – Precession is the actual change in the direction of the a climbing rate. plane of the rotation under the influence of an applied force.

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Lecture #1 Lecture #1 Gyroscopic Systems (2) Attitude Indicators

• Universally mounted (rotates free in any plane) • Horizon bar is attached to a gyro to remain parallel to natural horizon (Gyro acts as a pendulum)

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• Formerly called the Directional Gyro • Heading indicator is mounted vertically – Susceptible to precession errors

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Lecture #1 Lecture #1 Turn Coordinator or Turn-and-Slip Flight Control Systems Indicator • Displays rate and quality of turn • Elevators • Turn rate, bank angle, and velocity related when – Horizontal surfaces on tail of a/c that induce pitch performing a coordinated turn • • “Step on the ball” – Horizontal surfaces on wing of a/c that act in opposite directions to induce roll • – Vertical surface on tail of a/c that induces yaw • Trim Tabs – Supplemental surface on elevators, ailerons, and rudder than can be used to create “fingertip” requirement under continual control surface displacement 2/2/2004 ASE167M Lecture 1 19 2/2/2004 ASE167M Lecture 1 20 Lecture #1 Lecture #1 Flight Control Systems (2) Flight Control Systems (3)

• Flaps – increase lift – increase drag

Flaps

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Lecture #1 Lecture #1 Power Plant Systems (1) Power Plant Systems (2)

• Carburetor : Use Carburetor Heat • Magnetos Test L and R

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Manifold Pressure (MP) RPM Control Fuel Flow •Cowl Flaps • Propellers or Control Control – RPM controls Pitch of the propellers

RPM Control

Manifold Pressure Fuel Flow Control (MP) or Throttle Control

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Lecture #1 Lecture #1 Lab Schedule Flight 1 Briefing

• Orientation Flight: Expand familiarity and develop the basic concepts for a/c performance • Get the best rate-of-climb and best angle-of-climb and its respective velocities (Vx and Vy)

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• In theory we would have to get those •EOM: h

L x performances at a constant altitude ⇒ wait until ANGLE OF ATTACK b T α θ flight #5 V x γ w PITCH ANGLE O xh H=const FLIGHT PATH ANGLE

D xw – Relative Wind direction W x – x body direction E i b xh – x local horizon direction k x Read R/C at constant altitude  xV& = cosγ  & = γ hVsin  g VT& =+−−cos()ε α DW sin γ • We are going to climb and read R/C for several  W 0  g γ =++−()εα γ altitudes, velocities and power settings and we & TLWsin0 cos  WV will assume that they were read at H=const. WCT& =−

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Lecture #1 Lecture #1 Flight 1 Briefing (2) Flight 1 Briefing (3)

Event Rate of Climb Airspeed • Record airspeed MP = Manifold Pressure (“ of Hg) (ft/mim) (knots) •Plot dh/dt vs. V for 5 points in the flight (Steps 3 to 7). Fit data to Preflight Checklist; RPM = Max ; MP = Max 0 0 and rate of climb Takeoff (Rotate at 75 knots); Raise 0 75 2 Climb at 100 knots to 2000 ft MSL; Read R/C at 1800 ft; Set RPM = Max; 100 = = + + data for climbs and MP = Max R / C h& a0 a1V a2V Climb at 120 knots to 3000 ft. Read R/C at 2800 ft 120 descents. Climb at 85 knots to 4000 ft. Read R/C at 3800 ft 85 • Go to specified Climb at 70 knots to 5000 ft. Read R/C at 4800 ft 70 – Use a least squares curve fit (available on most plotting Climb at 65 knots to 6000 ft. Read R/C at 5800 ft 65 packages) airspeed, allow time Level off at 6000 ft. Set and Stabilize for 1 mim. Read Airspeed 0 Reduce RPM = 2300; MP = 21 “Hg. Read Airspeed after stabilized 0 for VVI to stabilize Reduce RPM = 2000; MP = 20 “Hg. Read Airspeed after stabilized 0 Set RPM = 2400; MP = Max. Read Airspeed after stabilized. 0 dh = γ (to ensure steady • Calculate max h& max and from parabolic constants and Lower ½ flaps. Read Airspeed after stabilized 0 dt max state reading of Lower Full flaps. Read Airspeed after stabilized. Raise ½ flaps and then retract 0 all flaps. from graphical representation data). Set RPM = 1800, MP = 17 “ Hg; adjust pitch for 120 knots descending. 120 h Descend to 4000 ft. Read R/C at 4200 ft. Adjust pitch for 100 knots. Descend to 3000 ft. Read R/C at 3100 ft. 100 h Adjust pitch for 90 knots. Record R/C, then Lower ½ flaps. 90 xb Set RPM = 1500; MP = 15 “Hg; Adjust pitch for 80 knots. Descend to 1000 ft 80 h h max MSL. Note R/C γ V Lower Full Flaps. Set RPM = Min., MP = Min. Descend at 80 knots. Read 80 R/C Lower Landing Gear. Continue Descent to landing 80 x Accomplish shutdown checklist 0 γ max x x 2/2/2004 ASE167M Lecture 1 31 2/2/2004 ASE167M Lecture 1 32 Lecture #1 Lecture #1 Flight 1 Briefing (4) Flight 1 Briefing (5) • Calculate theoretical max dh/dt by solving: • Why does this provide max γ? ∂ – In this a/c -900< γ <900 so that h& = a + 2a V = 0 ∂V 1 2 max γ = max sin(γ) γ • Calculate theoretical max by solving: h& a sin()γ = = 0 + a + a V = m V V 1 2 R / C = h& = V sinγ ∂ γ ∂  h&  a – Note that this also has a linear geometrical ()sin =   = − 0 + a = 0   2 2 ∂V ∂V V  V interpretation.

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Lecture #1 Lecture #1 Flight 1 Briefing (7) Lab Administration • Report: • Reports – Answer 4 questions in lab manual, put in either Discussion or Test Results section. – Groups of 5 –Plot h vs. x (use intuitive x, since ground distance is – Individual Work and Lab Reports not actually measured). – Due in two weeks – Discuss the effects of flaps on the lift and drag characteristics of the a/c. What is the purpose of • Look at the website for procedures flaps? And… • Look at the website for Schedule (When – look at report requirements on the web and in lab should I fly?) manual – Fly after a briefing class – include every section – Do not hesitate to ask questions …

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Flight 1 – Orientation Flight Report Due: 02/16

Next Week: The Atmosphere Computer Project 1

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