894:
20:
645:
534:
134:
is 906 kilometres per hour (489 kn). The speed of sound increases with air temperature, so at Mach 0.83 at 3,000 m (10,000 ft) where the air is much warmer than at 9,100 m (30,000 ft), the true airspeed at
649:
344:
434:
570:
374:
412:
688:
593:
428:
When a shock wave forms across the pitot tube the required formula is derived from the
Rayleigh Supersonic Pitot equation, and is solved iteratively:
629:
935:
838:
634:. U.S. Government Printing Office, Washington D.C.: U.S. Federal Aviation Administration. 2007. pp. 3–10. FAA-H-8083-15A. Archived from
858:
101:. Therefore, indicated airspeed is not entirely adequate to warn the pilot of the impending problems. Mach number is more useful, and most
843:
177:
123:
624:. U.S. Government Printing Office, Washington D.C.: U.S. Federal Aviation Administration. 2005-11-25. pp. 3–8. FAA-H-8083-15.
163:
capsule which together convert pitot-static pressure into Mach number. The
Machmeter suffers from instrument and position errors.
833:
681:
959:
797:
756:
954:
928:
674:
802:
792:
817:
660:
705:
89:
number, where air flowing over low-pressure areas of its surface locally reaches the speed of sound, forming
969:
761:
964:
921:
863:
654:
635:
58:
812:
529:{\displaystyle {M}=0.88128485{\sqrt {{\frac {p_{t}}{p}}\left(1-{\frac {1}{}}\right)^{\frac {5}{2}}}}}
608:
581:
573:
421:
152:
39:
787:
746:
718:
697:
598:
160:
94:
751:
148:
102:
42:
905:
545:
766:
66:
355:
69:. An aircraft flying at the speed of sound is flying at a Mach number of one, expressed as
853:
415:
386:
394:
122:
is Mach 0.83, then at 9,100 m (30,000 ft) where the speed of sound under
771:
54:
948:
848:
127:
86:
50:
97:
for this condition changes with ambient temperature, which in turn changes with
603:
62:
24:
873:
728:
90:
738:
713:
156:
82:
893:
901:
868:
98:
36:
807:
19:
666:
46:
18:
594:
171:
In subsonic flow the Mach meter can be calibrated according to:
670:
339:{\displaystyle {M}={\sqrt {5\left}}\,or,{M}={\sqrt {5\left}}\,}
105:
are limited to a maximum operating Mach number, also known as
584:
and static pressure. Air temperature input is not required.
85:
flight approaches the speed of sound, it first reaches its
909:
23:
Illustration showing the face of a
Machmeter reading a
548:
437:
397:
358:
180:
147:
Modern electronic
Machmeters use information from an
826:
780:
737:
704:
155:. Some older mechanical Machmeters use an altitude
564:
528:
406:
368:
338:
126:is 1,093 kilometres per hour (590 kn), the
929:
682:
151:which makes calculations using inputs from a
8:
936:
922:
689:
675:
667:
556:
547:
513:
496:
480:
457:
451:
449:
438:
436:
396:
365:
357:
335:
311:
296:
290:
275:
267:
257:
233:
211:
205:
189:
181:
179:
139:would be 982 km/h (530 kn).
65:. This is shown on a Machmeter as a
7:
890:
888:
859:Integrated standby instrument system
908:. You can help Knowledge (XXG) by
580:Note that the inputs required are
14:
576:measured behind the normal shock.
892:
834:Air data inertial reference unit
648: This article incorporates
643:
798:Horizontal situation indicator
757:Horizontal situation indicator
502:
486:
1:
986:
887:
803:Inertial navigation system
793:Course deviation indicator
656:Instrument Flying Handbook
631:Instrument Flying Handbook
622:Instrument Flying Handbook
661:United States Government
149:air data computer system
762:Turn and slip indicator
565:{\displaystyle \ p_{t}}
422:ratio of specific heats
904:-related article is a
864:Primary flight display
650:public domain material
566:
530:
408:
370:
340:
59:dimensionless quantity
28:
960:Measuring instruments
567:
531:
409:
371:
369:{\displaystyle \ M\,}
341:
22:
955:Aircraft instruments
813:Satellite navigation
546:
435:
395:
356:
178:
115:For example, if the
609:Pitot-static system
407:{\displaystyle \ p}
153:pitot-static system
124:standard conditions
103:high-speed aircraft
40:pitot-static system
788:Aircraft periscope
747:Attitude indicator
719:Airspeed indicator
698:Flight instruments
599:Airspeed indicator
562:
526:
404:
389:(dynamic pressure)
366:
336:
95:indicated airspeed
81:As an aircraft in
29:
917:
916:
882:
881:
752:Heading indicator
551:
524:
521:
506:
466:
420:and assuming the
400:
361:
333:
319:
305:
255:
241:
220:
43:flight instrument
16:Flight instrument
977:
938:
931:
924:
896:
889:
808:Magnetic compass
767:Turn coordinator
691:
684:
677:
668:
664:
647:
646:
639:
625:
571:
569:
568:
563:
561:
560:
549:
535:
533:
532:
527:
525:
523:
522:
514:
512:
508:
507:
505:
501:
500:
481:
467:
462:
461:
452:
450:
442:
413:
411:
410:
405:
398:
375:
373:
372:
367:
359:
345:
343:
342:
337:
334:
332:
328:
321:
320:
312:
310:
306:
301:
300:
291:
276:
271:
256:
254:
250:
243:
242:
234:
232:
228:
221:
216:
215:
206:
190:
185:
67:decimal fraction
985:
984:
980:
979:
978:
976:
975:
974:
945:
944:
943:
942:
885:
883:
878:
854:Head-up display
822:
776:
733:
700:
695:
653:
644:
628:
620:
617:
590:
552:
544:
543:
492:
485:
473:
469:
468:
453:
433:
432:
416:static pressure
393:
392:
387:impact pressure
383:
354:
353:
292:
286:
285:
284:
280:
207:
204:
200:
199:
198:
194:
176:
175:
169:
145:
138:
133:
120:
110:
79:
45:that shows the
17:
12:
11:
5:
983:
981:
973:
972:
970:Aviation stubs
967:
962:
957:
947:
946:
941:
940:
933:
926:
918:
915:
914:
897:
880:
879:
877:
876:
871:
866:
861:
856:
851:
846:
841:
836:
830:
828:
827:Related topics
824:
823:
821:
820:
815:
810:
805:
800:
795:
790:
784:
782:
778:
777:
775:
774:
772:Turn indicator
769:
764:
759:
754:
749:
743:
741:
735:
734:
732:
731:
726:
721:
716:
710:
708:
702:
701:
696:
694:
693:
686:
679:
671:
641:
640:
638:on 2008-04-22.
626:
616:
613:
612:
611:
606:
601:
596:
589:
586:
582:total pressure
578:
577:
574:total pressure
559:
555:
537:
536:
520:
517:
511:
504:
499:
495:
491:
488:
484:
479:
476:
472:
465:
460:
456:
448:
445:
441:
426:
425:
418:
403:
390:
381:
377:
376:is Mach number
364:
347:
346:
331:
327:
324:
318:
315:
309:
304:
299:
295:
289:
283:
279:
274:
270:
266:
263:
260:
253:
249:
246:
240:
237:
231:
227:
224:
219:
214:
210:
203:
197:
193:
188:
184:
168:
165:
144:
141:
136:
131:
118:
108:
78:
75:
55:speed of sound
15:
13:
10:
9:
6:
4:
3:
2:
982:
971:
968:
966:
965:Speed sensors
963:
961:
958:
956:
953:
952:
950:
939:
934:
932:
927:
925:
920:
919:
913:
911:
907:
903:
898:
895:
891:
886:
875:
872:
870:
867:
865:
862:
860:
857:
855:
852:
850:
849:Glass cockpit
847:
845:
842:
840:
837:
835:
832:
831:
829:
825:
819:
816:
814:
811:
809:
806:
804:
801:
799:
796:
794:
791:
789:
786:
785:
783:
779:
773:
770:
768:
765:
763:
760:
758:
755:
753:
750:
748:
745:
744:
742:
740:
736:
730:
727:
725:
722:
720:
717:
715:
712:
711:
709:
707:
703:
699:
692:
687:
685:
680:
678:
673:
672:
669:
665:
662:
658:
657:
651:
637:
633:
632:
627:
623:
619:
618:
614:
610:
607:
605:
602:
600:
597:
595:
592:
591:
587:
585:
583:
575:
557:
553:
542:
541:
540:
518:
515:
509:
497:
493:
489:
482:
477:
474:
470:
463:
458:
454:
446:
443:
439:
431:
430:
429:
423:
419:
417:
401:
391:
388:
384:
378:
362:
352:
351:
350:
329:
325:
322:
316:
313:
307:
302:
297:
293:
287:
281:
277:
272:
268:
264:
261:
258:
251:
247:
244:
238:
235:
229:
225:
222:
217:
212:
208:
201:
195:
191:
186:
182:
174:
173:
172:
166:
164:
162:
158:
154:
150:
142:
140:
129:
128:true airspeed
125:
121:
113:
111:
104:
100:
96:
92:
88:
87:critical mach
84:
76:
74:
72:
68:
64:
60:
56:
52:
51:true airspeed
48:
44:
41:
38:
34:
26:
21:
910:expanding it
899:
884:
781:Navigational
723:
706:Pitot-static
655:
642:
636:the original
630:
621:
579:
538:
427:
379:
348:
170:
146:
116:
114:
106:
80:
70:
32:
30:
604:Mach number
167:Calibration
91:shock waves
71:Mach 1
63:Mach number
25:Mach number
949:Categories
874:Yaw string
739:Gyroscopic
729:Variometer
615:References
447:0.88128485
724:Machmeter
714:Altimeter
478:−
323:−
245:−
143:Operation
83:transonic
33:Machmeter
902:aviation
869:V speeds
588:See also
161:airspeed
99:altitude
37:aircraft
572:is now
539:where:
349:where:
159:and an
157:aneroid
61:called
53:to the
49:of the
27:of 0.83
550:
424:is 1.4
399:
360:
93:. The
35:is an
900:This
652:from
57:, a
47:ratio
906:stub
844:EFIS
839:ECAM
818:SIGI
130:at M
414:is
385:is
77:Use
951::
659:.
137:MO
132:MO
119:MO
112:.
109:MO
73:.
31:A
937:e
930:t
923:v
912:.
690:e
683:t
676:v
663:.
558:t
554:p
519:2
516:5
510:)
503:]
498:2
494:M
490:7
487:[
483:1
475:1
471:(
464:p
459:t
455:p
444:=
440:M
402:p
382:c
380:q
363:M
330:]
326:1
317:7
314:2
308:)
303:p
298:t
294:p
288:(
282:[
278:5
273:=
269:M
265:,
262:r
259:o
252:]
248:1
239:7
236:2
230:)
226:1
223:+
218:p
213:c
209:q
202:(
196:[
192:5
187:=
183:M
135:M
117:M
107:M
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