343:
229:
122:
380:
25:
241:
293:(left limit line in the diagram). As the aircraft gains altitude the stall speed increases; since the wing is not growing any larger the only way to support the aircraft's weight with less air is to increase speed. While the exact numbers will vary widely from aircraft to aircraft, the nature of this relationship is typically the same; plotted on a graph of speed (x-axis) vs. altitude (y-axis) it forms a diagonal line.
202:
In overall terms this is very little extra power, 60% of the engine's output is already used up just keeping the plane in the air. The leftover 40 hp is all that the aircraft has to maneuver with, meaning it can climb, turn, or speed up only a small amount. To put this in perspective, the C150 could not maintain a 2
326:
The right side of the graph represents the maximum speed of the aircraft. This is typically sloped in the same manner as the stall line due to air resistance getting lower at higher altitudes, up to the point where an increase in altitude no longer increases the maximum speed due to lack of oxygen to
201:
at 2,500-foot (760 m) altitude and 90-mile-per-hour (140 km/h) speed needs about 60 horsepower (45 kW) to fly straight and level. The C150 is normally equipped with a 100-horsepower (75 kW) engine, so in this particular case the plane has 40 horsepower (30 kW) of extra power.
440:
Although it is easy to compare aircraft on simple numbers such as maximum speed or service ceiling, an examination of the flight envelope will reveal far more information. Generally a design with a larger area under the curve will have better all-around performance. This is because when the plane is
517:
272:
Flying outside the envelope is possible, since it represents the straight-and-level condition only. For instance diving the aircraft allows higher speeds, using gravity as a source of additional power. Likewise higher altitude can be reached by first speeding up and then going ballistic, a maneuver
164:
The term is somewhat loosely applied, and can also refer to other measurements such as maneuverability. For example, when a plane is pushed, for instance by diving it at high speeds, it is said to be flown "outside the envelope", something considered rather dangerous. During vehicle test programs,
365:
At higher temperatures, air is less dense and planes must fly faster to generate the same amount of lift. High heat may reduce the amount of cargo a plane can carry, increase the length of runway a plane needs to take off, and make it more difficult to avoid obstacles such as mountains. In unusual
445:
aircraft have very small flight envelopes, with speeds ranging from perhaps 50 to 200 mph, whereas the extra power available to modern fighter aircraft result in huge flight envelopes with many times the area. As a trade-off however, military aircraft often have a higher stalling speed. As a
256:
The outer edges of the diagram, the envelope, show the possible conditions that the aircraft can reach in straight and level flight. For instance, the aircraft described by the black altitude envelope on the right can fly at altitudes up to about 52,000 feet (16,000 m), at which point the
252:
A doghouse plot generally shows the relation between speed at level flight and altitude, although other variables are also possible. It takes more effort to make than an extra power calculation, but in turn provides much more information such as ideal flight altitude. The plot typically looks
264:
In the case of high-performance aircraft, including fighters, this "1-g" line showing straight-and-level flight is augmented with additional lines showing the maximum performance at various g loadings. In the diagram at right, the green line represents, 2-g, the blue line 3-g, and so on. The
215:
might require considerably more power due to their wings being designed for high speed, high agility, or both. It could require 10,000 horsepower (7.5 MW) to achieve similar performance. However modern jet engines can provide considerable power with the equivalent of 50,000 horsepower
253:
something like an upside-down U and is commonly referred to as a doghouse plot due to its resemblance to a kennel (sometimes known as a 'doghouse' in
American English). The diagram on the right shows a very simplified plot which shall be used to explain the general shape of the plot.
168:
Flight envelope is one of a number of related terms that are used in a similar fashion. It is perhaps the most common term because it is the oldest, first being used in the early days of test flight. It is closely related to more modern terms known as
177:
which are different ways of describing the flight envelope of an aircraft. In addition, the term has been widened in scope outside the field of engineering, to refer to the strict limits in which an event will take place or more generally to the
165:
flight envelope simply means that part of the aircraft or spacecraft's design capabilities that have already been successfully tested, and have therefore moved from theoretical or designed capability into a demonstrated/certified capability.
557:
461:
This phrase is used to refer to an aircraft being taken to or beyond its designated altitude and speed limits. By extension, this phrase may be used to mean testing other limits, either within aerospace or in other fields e.g.
514:
261:. All of the area under the curve represents conditions that the plane can fly at with power to spare, for instance, this aircraft can fly at Mach 0.5 at 30,000 feet (9,100 m) while using less than full power.
301:
Inefficiencies in the wings also make this line "tilt over" with increased altitude, until it becomes horizontal and additional speed will not result in increased altitude. This maximum altitude is known as the
194:, is a very basic method of determining an aircraft's flight envelope. It is easily calculated but as a downside does not tell very much about the actual performance of the aircraft at different altitudes.
334:
means that it varies with the square of speed—in other words it is typically easier to go higher than faster, up to the altitude where lack of oxygen for the engines starts to play a significant role.
362:
A chart of velocity versus load factor (or V-n diagram) is another way of showing limits of aircraft performance. It shows how much load factor can be safely achieved at different airspeeds.
554:
306:(top limit line in the diagram), and is often quoted for aircraft performance. The area where the altitude for a given speed can no longer be increased at level flight is known as
257:
thinner air means it can no longer climb. The aircraft can also fly at up to Mach 1.1 at sea level, but no faster. This outer surface of the curve represents the
441:
not flying at the edges of the envelope, its extra power will be greater, and that means more power for things like climbing or maneuvering.
535:
197:
Choosing any particular set of parameters will generate the needed power for a particular aircraft for those conditions. For instance a
366:
weather conditions this may make it unsafe or uneconomical to fly, occasionally resulting in the cancellation of commercial flights.
480:
89:
61:
579:
566:
68:
427:
245:
108:
409:
401:
42:
75:
646:
641:
405:
46:
656:
651:
208:(20 m/s²) turn, which would require a minimum of 120 horsepower (89 kW) under the same conditions.
590:
216:(37 MW) not being atypical. With this amount of extra power the aircraft can achieve very high maximum
57:
455:
158:
475:
390:
394:
269:
has a very small area just below Mach 1 and close to sea level where it can maintain a 9-g turn.
35:
532:
82:
580:
Why planes can’t fly when it’s too hot, and other ways our civilization can’t take the heat
266:
8:
286:
220:, even climb straight up, make powerful continual maneuvers, or fly at very high speeds.
618:
463:
490:
485:
442:
212:
561:
539:
521:
303:
314:
of the aircraft getting smaller at higher altitudes, until it no longer exceeds
602:
331:
635:
217:
311:
130:
555:"The Army Aviator's Handbook for Manoeuvring Flight and Power Management"
495:
342:
330:
The power needed varies almost linearly with altitude, but the nature of
290:
274:
228:
198:
150:
182:
of a given phenomenon or situation, and hence, its "flight envelope".
121:
379:
24:
240:
154:
146:
289:
have a minimum speed at which they can maintain level flight, the
315:
203:
454:"Pushing the envelope" redirects here. For the album, see
161:
or atmospheric density, often simplified to altitude.
449:
153:refers to the capabilities of a design in terms of
49:. Unsourced material may be challenged and removed.
446:result of this, the landing speed is also higher.
248:(doghouse plot). Contour is specific excess power.
337:
633:
16:Aerodynamic performance of an air or spacecraft
408:. Unsourced material may be challenged and
570:, 24 March 2005. Accessed: 6 January 2011.
428:Learn how and when to remove this message
109:Learn how and when to remove this message
341:
239:
227:
120:
549:
547:
634:
595:
233:
625:, 6 May 2014. Accessed: 16 May 2014.
591:Why Planes Can't Fly In Extreme Heat
544:
406:adding citations to reliable sources
373:
244:Turn rate envelope, described in an
47:adding citations to reliable sources
18:
617:G.W. Poulos & Daniel Lindley. "
13:
567:United States Army Aviation Branch
481:Helicopter height–velocity diagram
296:
14:
668:
280:
236:diagram). Contour is load factor.
378:
223:
23:
34:needs additional citations for
611:
584:
573:
526:
508:
338:Velocity vs. load factor chart
185:
1:
369:
354:(corner/maneuver speed) and V
456:Pushing the Envelope (album)
321:
7:
608:. Accessed: 6 January 2011.
469:
10:
673:
619:What Is a Flight Envelope?
453:
259:zero-extra-power condition
211:For the same conditions a
533:Flight envelope – diagram
501:
476:Coffin corner (aviation)
125:Flight envelope diagram.
515:§23.333 Flight envelope
346:A V-n diagram showing V
450:"Pushing the envelope"
359:
350:(stall speed at 1G), V
249:
237:
126:
647:Aircraft aerodynamics
642:Aerospace engineering
538:June 1, 2010, at the
345:
310:and is caused by the
243:
231:
192:specific excess power
124:
657:Aircraft performance
652:Aircraft wing design
553:Sinclair, Edward J.
402:improve this section
267:F-16 Fighting Falcon
180:predictable behavior
143:performance envelope
43:improve this article
287:fixed-wing aircraft
232:Altitude envelope (
601:Quinion, Michael.
560:2011-07-17 at the
520:2012-04-02 at the
464:Plus ultra (motto)
360:
327:feed the engines.
308:zero rate of climb
250:
238:
127:
603:Push the envelope
438:
437:
430:
119:
118:
111:
93:
58:"Flight envelope"
664:
626:
615:
609:
606:World Wide Words
599:
593:
588:
582:
577:
571:
551:
542:
530:
524:
512:
491:Maneuvring speed
443:General aviation
433:
426:
422:
419:
413:
382:
374:
235:
213:fighter aircraft
190:Extra power, or
139:service envelope
114:
107:
103:
100:
94:
92:
51:
27:
19:
672:
671:
667:
666:
665:
663:
662:
661:
632:
631:
630:
629:
616:
612:
600:
596:
589:
585:
578:
574:
562:Wayback Machine
552:
545:
540:Wayback Machine
531:
527:
522:Wayback Machine
513:
509:
504:
472:
459:
452:
434:
423:
417:
414:
399:
383:
372:
357:
353:
349:
340:
324:
304:service ceiling
299:
297:Service ceiling
283:
226:
188:
135:flight envelope
115:
104:
98:
95:
52:
50:
40:
28:
17:
12:
11:
5:
670:
660:
659:
654:
649:
644:
628:
627:
610:
594:
583:
572:
543:
525:
506:
505:
503:
500:
499:
498:
493:
488:
486:KĂĽssner effect
483:
478:
471:
468:
451:
448:
436:
435:
386:
384:
377:
371:
368:
355:
351:
347:
339:
336:
323:
320:
298:
295:
282:
281:Stalling speed
279:
225:
222:
187:
184:
117:
116:
31:
29:
22:
15:
9:
6:
4:
3:
2:
669:
658:
655:
653:
650:
648:
645:
643:
640:
639:
637:
624:
620:
614:
607:
604:
598:
592:
587:
581:
576:
569:
568:
563:
559:
556:
550:
548:
541:
537:
534:
529:
523:
519:
516:
511:
507:
497:
494:
492:
489:
487:
484:
482:
479:
477:
474:
473:
467:
465:
457:
447:
444:
432:
429:
421:
411:
407:
403:
397:
396:
392:
387:This section
385:
381:
376:
375:
367:
363:
344:
335:
333:
328:
319:
317:
313:
309:
305:
294:
292:
288:
278:
276:
270:
268:
262:
260:
254:
247:
242:
230:
224:Doghouse plot
221:
219:
218:rate of climb
214:
209:
207:
206:
200:
195:
193:
183:
181:
176:
175:doghouse plot
172:
166:
162:
160:
156:
152:
148:
144:
140:
136:
132:
123:
113:
110:
102:
91:
88:
84:
81:
77:
74:
70:
67:
63:
60: –
59:
55:
54:Find sources:
48:
44:
38:
37:
32:This article
30:
26:
21:
20:
622:
613:
605:
597:
586:
575:
565:
528:
510:
460:
439:
424:
415:
400:Please help
388:
364:
361:
358:(dive speed)
329:
325:
307:
300:
284:
271:
263:
258:
255:
251:
210:
204:
196:
191:
189:
179:
174:
170:
167:
163:
142:
138:
134:
131:aerodynamics
128:
105:
96:
86:
79:
72:
65:
53:
41:Please help
36:verification
33:
496:Corner case
291:stall speed
273:known as a
246:E-M diagram
186:Extra power
171:extra power
159:load factor
636:Categories
370:Side notes
275:zoom climb
199:Cessna 150
151:spacecraft
69:newspapers
564:. p. 25.
418:June 2024
389:does not
322:Top speed
99:June 2009
623:WiseGeek
558:Archived
536:Archived
518:Archived
470:See also
155:airspeed
147:aircraft
410:removed
395:sources
316:gravity
83:scholar
173:and a
145:of an
133:, the
85:
78:
71:
64:
56:
502:Notes
141:, or
90:JSTOR
76:books
393:any
391:cite
332:drag
312:lift
285:All
157:and
62:news
404:by
234:H-M
149:or
129:In
45:by
638::
621:"
546:^
466:.
318:.
277:.
137:,
458:.
431:)
425:(
420:)
416:(
412:.
398:.
356:D
352:C
348:S
205:g
112:)
106:(
101:)
97:(
87:·
80:·
73:·
66:·
39:.
Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.
