Download presentation

Presentation is loading. Please wait.

Published byDarrion Homan Modified over 2 years ago

1
Aero Engineering 315 Lesson 25 Performance— Power Required and Power Available

2
Air Force Developmental Education (DE) — formerly known as Professional Military Education (PME) Step 1: Aerospace Basic Course (ASBC) Maxwell AFB, AL – six weeks All second lieutenants (first year of service) In-residence program Ungraded course/no DG program Airpower history/theory/operations, communication skills, leadership/problem solving/teambuilding Physical training, obstacle course Wargame

3
Air Force Developmental Education (DE) Step 2: Squadron Officer School (SOS) Captains (4-7 years of service) Offered via correspondence (after pin-on), in-residence Competitive selection for in-residence (75%+, alternates) In-residence program: Maxwell AFB, AL – five weeks Graded course/DG program (overall performance) Airpower history/theory/operations, communication skills, officership/problem solving/teambuilding MC tests, graded briefings, graded position paper Physical training, volleyball, flickerball, Project X Wargame Flight competition

4
Air Force Developmental Education (DE) Step 3: Intermediate Developmental Education (IDE)—formerly known as Intermediate Service School (ISS) Majors Multiple options Air Command and Staff College (ACSC)—offered via correspondence/seminar (after selection), in-residence In-residence program: Maxwell AFB, AL – 10 months Graded course/DG program (academic performance) Softball Advanced academic degree (e.g. AFIT) Advanced Study of Air Mobility (ASAM) Air Force Intern Program (AFIP) Sister service/foreign schools IDE in-residence candidacy determined by O-4 promotion board (~30%)

5
Air Force Developmental Education (DE) Step 4: Senior Developmental Education (SDE)—formerly known as Senior Service School (SSS) Lieutenant colonels Multiple options Air War College (AWC)—offered via correspondence (after selection), in-residence In-residence program: Maxwell AFB, AL – 1 year Industrial College of the Armed Forces (ICAF) – 1 year Various fellowship programs National War College/sister service schools/foreign schools SDE in-residence candidacy determined by O-5 promotion board (~20%?)

6
Air Force Developmental Education (DE) Why do I care? Without SOS (IPZ): 0% selection! Selection Rate (CY02B) PRF BPZ IPZ APZ DP n/a 100% 100% P n/a 79.8% 4.3% Total n/a 92.6% 7.8%

7
Air Force Developmental Education (DE) Without ISS (IPZ): 0% selection! Without SSS (IPZ): 2% selection!

8
Additional Example: T-38 At Sea Level: 1.What is (L/D) MAX for 8,000 lb? 2.What is the Parasite Drag at (L/D) MAX for 8,000 lb? 3.For W=8,000 lb, what Mach range can I achieve using reverse command on the throttle (i.e. back side of curve)?

9
Power req’d & available objectives Sketch power required (P R ) & power available curves for a turbojet aircraft State the slope of a power available curve (T A ) Find min drag point on power required curve From a T-38 chart find P R, min P R, excess power, max excess power, max and min Mach Know relationship between induced & parasite drag at min P R From a drag polar calculate velocity for min P R Sketch T R and P R changes with wt, alt & configuration Know how parameters & velocities change with wt, alt & config Min drag, (L/D) max, and min P R

10
Thrust vs. Power vs. a Pickup

11
What is Power? Power and Work For aircraft Power = andWork = thereforePower = Force x Distance/Time orPower = Force x Velocity P A = T A V P R = T R V = DV Work / Time Force x Distance

12
V P PRPR P A (DRY) V MAX P R MIN V MIN Slope = rise/run = P A /V = T A Note: curve steepens at high velocities V P R MIN Power Required and Power Available versus Velocity

13
V P P R for a given V Slope = (P R /V) MIN = T R MIN = D MIN V T R MIN = V D MIN V P R MIN The slope of a line from the origin to any point on the P R curve is rise/run or P R /V = T R. So the point where the slope is minimized is the point of T R MIN or D MIN. V P R MIN < V T R MIN If this slope = T R, where is T R,MIN ?

14
T-38 Power Chart from Supplemental Data Sea Level P R for M= 0.8 = 2.15x10 6 ft-lbs/sec = 2.5x10 5 ft-lbs/sec At 0.325 Mach Min P R, W=8000 lbs

15
Min Power Required using Drag Polar So, at min P R : 3 x Parasite Drag = Drag due to Lift so: C D = C D,0 + C D,i = 4 C D,0 = 4 k C L 2 /3 Solving for C L : Thus: 3C D,0 = C D,i or 3C D,0 = k C L 2 C L = (3C D,0 /k) 1/2 T R = ½ V 2 S C D,0 + 2 kW 2 / ( V 2 S) P R = T R x V = ½ V 3 S C D,0 + 2 kW 2 / ( V S) dP R /dV = 3 ( ½ V 2 S C D,0 ) - 2 kW 2 / ( V 2 S) = 0 At Minimum P R

16
Example: T-37 again Using C D = 0.02 + 0.057C L 2 (from whole aircraft lesson), S = 184 ft 2 and W = 6,000 lb @ SL Find V @ P RMIN C L = (3C D,0 /k) 1/2 (at P Rmin ) L = 6,000 lbs = (3C D,0 /k) 1/2 ½ V 2 S so V = (12,000 / (3C D,0 /k) 1/2 S ) 1/2 C L = (3 0.02/0.057) ½ = 1.026 V = 163.5 ft/s

17
V P PRPR P A (DRY) PXPX Excess Power For a given velocity, say V 1 P X = Excess Power = P A – P R (@ V 1 ) V1V1

18
V P PRPR P A (DRY) P X MAX V P X MAX Maximum Excess Power Line parallel to P A and tangent to P R

19
Configuration Changes V T TRTR TATA V P P R P A “Dirty configuration” – increases C D o

20
Weight Changes V T TRTR TATA V P P R P A Increasing Weight

21
Altitude Changes V T TRTR TATA Increasing Altitude (Decreasing ) Less Parasite Drag More Drag from Lift T A = T SL SL

22
Altitude Changes P P R P A V Increasing Altitude (Decreasing )

23
Parameter Changes C D 0 W h D min V Dmin V max V min P Rmin V P Rmin L/D max T & P A A little TAS

24
Next Lesson (26)… Fighter Design Project Prior to class Read Handout! In Class Finish P R and P A material Discuss fighter design project Ask questions!!!

Similar presentations

OK

Review Chapter 12. Fundamental Flight Maneuvers Straight and Level Turns Climbs Descents.

Review Chapter 12. Fundamental Flight Maneuvers Straight and Level Turns Climbs Descents.

© 2018 SlidePlayer.com Inc.

All rights reserved.

Ads by Google

Ppt on as 14 amalgamation tape Ppt on complex numbers class 11th accounts Ppt on condition based maintenance definition Ppt on amplitude shift keying modem Ppt on nestle india ltd company Ppt on 3-phase squirrel cage induction motor Topics for ppt on current affairs Ppt on standing order forms Ppt on famous indian entrepreneurship Ppt on dot net basics