25:
73:
1609:
1818:
1377:
222:
rate, can create dangerous situations and accidents. Parachutes at higher altitudes fly more aggressively, making their effective area smaller, which is more demanding for a pilot's skill and can be especially dangerous for high-performance landings, which require accurate estimates and have a low
201:
The density altitude is an important factor in skydiving, and one that can be difficult to judge properly, even for experienced skydivers. In addition to the general change in wing efficiency that is common to all aviation, skydiving has additional considerations. There is an increased risk due to
1083:
1341:
1180:
157:
The power output of a normally-aspirated engine – the power output depends on the oxygen intake, so the engine output is reduced as the equivalent dry-air density decreases, and it produces even less power as moisture displaces oxygen in more humid
1604:{\displaystyle {\begin{aligned}{\text{DA}}&\approx {\text{PA}}+118.8~{\frac {\text{ft}}{^{\circ }{\text{C}}}}\left\\&=1.2376\,{\text{PA}}+118.8~{\frac {\text{ft}}{{}^{\circ }{\text{C}}}}\,T_{\text{OA}}-1782~{\text{ft}}.\end{aligned}}}
845:
1822:
395:
990:
1382:
1248:
1659:
1116:
880:
189:
Due to these performance issues, an aircraft's takeoff weight may need to be lowered, or takeoffs may need to be scheduled for cooler times of the day. The wind direction and the
119:, will cause an increase in the density altitude. In hot and humid conditions, the density altitude at a particular location may be significantly higher than the true altitude.
1700:
1241:
553:
478:
1204:
1111:
906:
423:
138:(TAS), are also subject to air-density changes. Furthermore, the power delivered by the aircraft's engine is affected by the density and composition of the atmosphere.
579:
702:
950:
928:
673:
643:
613:
516:
449:
231:
The density altitude can be calculated from the atmospheric pressure and the outside air temperature (assuming dry air) using the following formula:
1663:
96:
would be equal to the indicated air density at the place of observation. In other words, the density altitude is the air density given as a height
1847:
1734:
206:
with a completely different density altitude than they are used to, without being made consciously aware of it by the routine of calibrating to
237:
1804:
167:
1877:
1078:{\displaystyle {\text{DA}}\approx {\text{PA}}+118.8~{\frac {\text{ft}}{^{\circ }{\text{C}}}}\left(T_{\text{OA}}-T_{\text{ISA}}\right).}
171:
89:
59:
1708:
44:
Please help improve this article by looking for better, more reliable sources. Unreliable citations may be challenged and removed.
1336:{\textstyle T_{\text{ISA}}\approx 15~{{}^{\circ }{\text{C}}}-1.98~{{}^{\circ }{\text{C}}}\,{\frac {\text{PA}}{1000~{\text{ft}}}}}
122:
In aviation, the density altitude is used to assess an aircraft's aerodynamic performance under certain weather conditions. The
1795:
1872:
38:
1175:{\textstyle \approx {\text{station elevation in feet}}+27~{\frac {\text{ft}}{\text{mb}}}(1013~{\text{mb}}-{\text{QNH}})}
178:
disadvantage. The following effects result from a density altitude that is higher than the actual physical altitude:
33:
146:
Air density is perhaps the single most important factor affecting aircraft performance. It has a direct bearing on:
650:
1852:
1833:
693:
489:
856:
1827:
1640:
1620:
519:
24:
696:
uses the following dry-air approximation to the formula for the density altitude above in its standard:
1742:
211:
112:
97:
1219:
960:
Note that the NWS standard specifies that the density altitude should be rounded to the nearest 100
531:
456:
1187:
1801:
1625:
1094:
953:
889:
481:
406:
131:
1684:
1679:
AOPA Flight
Training, Volume 19, Number 4; April 2007; Aircraft Owners and Pilots Association;
182:
An aircraft will accelerate more slowly on takeoff as a result of its reduced power production.
1680:
493:
215:
101:
564:
840:{\displaystyle {\text{DA}}_{\text{NWS}}=145442.16~{\text{ft}}\left(1-\left^{0.235}\right).}
1808:
1771:. Departments of the Air Force and Navy. 1 December 1989. AFM 51-40 / NAVAIR 00-80V-49.
1630:
935:
913:
658:
628:
598:
501:
434:
93:
1866:
968:
Approximation formula for calculating the density altitude from the pressure altitude
485:
135:
1635:
620:
163:
123:
1776:
218:
at high density altitudes, which, combined especially with the unexpected higher
1857:
883:
680:
203:
175:
108:
185:
An aircraft will climb more slowly as a result of its reduced power production.
150:
The efficiency of a propeller or rotor – which for a propeller (effectively an
72:
1352:
1207:
586:
930:, station pressure (static atmospheric pressure) in inches of mercury (inHg);
1211:
219:
390:{\displaystyle {\text{DA}}\approx {\frac {T_{\text{SL}}}{\Gamma }}\left.}
116:
85:
484:
atmospheric pressure, International
Standard Atmosphere (ISA): 1013.25
151:
127:
972:
This is an easier formula to calculate (with great approximation) the
1343:, assuming that the outside air temperature falls at the rate of 1.98
523:
426:
190:
71:
1802:
http://www.tpub.com/content/aerographer/14269/css/14269_74.htm
1660:"AC 00-45H - Aviation Weather Services – Document Information"
207:
18:
202:
the high mobility of jumpers (who will often travel to a
100:. The density altitude can also be considered to be the
1251:
1119:
1380:
1222:
1190:
1097:
993:
938:
916:
892:
859:
705:
661:
631:
601:
567:
534:
504:
459:
437:
409:
240:
16:
Altitude relative to standard atmospheric conditions
952:, station temperature (outside air temperature) in
115:, and, to a much lesser degree, an increase in the
1853:Density Altitude influence on aircraft performance
1603:
1335:
1243:, outside air temperature in degrees Celsius (°C);
1235:
1198:
1174:
1105:
1077:
944:
922:
900:
874:
839:
667:
637:
607:
573:
547:
510:
472:
443:
417:
389:
214:). Another factor is the higher susceptibility to
1735:"High and Fast: Understanding Density Altitude"
882:, National Weather Service density altitude in
223:margin of error before they become dangerous.
8:
1694:
1692:
1371:°C, this approximation simplifies to become
1829:Pilot's Handbook of Aeronautical Knowledge
1792:Pilot's Handbook of Aeronautical Knowledge
1728:
1726:
688:The National Weather Service (NWS) formula
1589:
1574:
1569:
1561:
1555:
1553:
1546:
1532:
1531:
1507:
1501:
1497:
1482:
1476:
1472:
1464:
1452:
1443:
1426:
1420:
1411:
1397:
1385:
1381:
1379:
1325:
1313:
1312:
1306:
1300:
1298:
1296:
1281:
1275:
1273:
1271:
1256:
1250:
1227:
1221:
1191:
1189:
1164:
1156:
1137:
1123:
1118:
1098:
1096:
1061:
1048:
1031:
1025:
1016:
1002:
994:
992:
937:
915:
893:
891:
866:
861:
858:
823:
803:
797:
795:
793:
781:
767:
761:
755:
727:
712:
707:
704:
660:
630:
600:
566:
539:
533:
503:
464:
458:
436:
410:
408:
368:
337:
330:
317:
308:
297:
288:
282:
255:
249:
241:
239:
193:slope may need to be taken into account.
104:adjusted for a non-standard temperature.
60:Learn how and when to remove this message
875:{\displaystyle {\text{DA}}_{\text{NWS}}}
1651:
154:) behaves similarly to lift on a wing.
7:
1675:
1673:
1777:"Air Density and Density Altitude"
568:
348:
261:
76:Density Altitude Computation Chart
14:
1113:, pressure altitude in feet (ft)
559:K, ISA sea-level air temperature;
1821: This article incorporates
1816:
451:, (static) atmospheric pressure;
23:
1796:Federal Aviation Administration
130:, and the relation between its
90:standard atmospheric conditions
1858:NewByte Atmospheric Calculator
1169:
1147:
1:
1790:Advisory Circular AC 61-23C,
1236:{\displaystyle T_{\text{OA}}}
548:{\displaystyle T_{\text{SL}}}
473:{\displaystyle P_{\text{SL}}}
1199:{\displaystyle {\text{QNH}}}
162:Aircraft taking off from a “
126:generated by the aircraft's
1848:Density Altitude Calculator
1106:{\displaystyle {\text{PA}}}
901:{\displaystyle {\text{ft}}}
418:{\displaystyle {\text{DA}}}
1894:
1878:Atmospheric thermodynamics
1206:, atmospheric pressure in
651:gravitational acceleration
1351:ft of altitude until the
1125:station elevation in feet
982:ISA temperature deviation
1834:United States Government
694:National Weather Service
490:U.S. Standard Atmosphere
107:Both an increase in the
1701:"Tragedy in Antarctica"
1641:List of longest runways
1621:Outside air temperature
574:{\displaystyle \Gamma }
520:outside air temperature
174:, are at a significant
166:” airport, such as the
32:Some of this article's
1823:public domain material
1733:Walker-Radtke, Megan.
1605:
1337:
1237:
1200:
1176:
1107:
1079:
946:
924:
902:
876:
841:
669:
639:
609:
587:temperature lapse rate
575:
549:
512:
474:
445:
425:, density altitude in
419:
391:
111:and a decrease in the
77:
1873:Altitudes in aviation
1606:
1338:
1238:
1201:
1177:
1108:
1080:
947:
925:
903:
877:
842:
670:
640:
610:
576:
550:
513:
475:
446:
420:
392:
75:
1699:Farnsworth, Musika.
1378:
1249:
1220:
1188:
1117:
1095:
991:
936:
914:
890:
857:
703:
659:
629:
599:
565:
532:
502:
457:
435:
407:
238:
113:atmospheric pressure
98:above mean sea level
1807:2008-09-19 at the
1745:on 15 January 2015
1739:Parachutist Online
1711:on 15 January 2015
1705:Parachutist Online
1626:Barometric formula
1601:
1599:
1333:
1233:
1196:
1172:
1103:
1075:
954:degrees Fahrenheit
942:
920:
898:
872:
837:
665:
635:
621:ideal gas constant
605:
571:
545:
508:
482:standard sea-level
470:
441:
415:
387:
132:indicated airspeed
78:
1592:
1588:
1577:
1567:
1564:
1550:
1545:
1535:
1510:
1496:
1485:
1470:
1467:
1463:
1456:
1446:
1432:
1429:
1415:
1410:
1400:
1388:
1331:
1328:
1324:
1317:
1309:
1295:
1284:
1270:
1259:
1230:
1210:(mb) adjusted to
1194:
1167:
1159:
1155:
1145:
1144:
1141:
1136:
1126:
1101:
1088:In this formula,
1064:
1051:
1037:
1034:
1020:
1015:
1005:
997:
978:pressure altitude
945:{\displaystyle T}
923:{\displaystyle P}
896:
869:
864:
850:In this formula,
816:
806:
792:
780:
776:
775:
770:
754:
730:
726:
715:
710:
668:{\displaystyle M}
638:{\displaystyle g}
608:{\displaystyle R}
542:
511:{\displaystyle T}
494:inches of mercury
467:
444:{\displaystyle P}
413:
400:In this formula,
355:
324:
320:
300:
264:
258:
244:
102:pressure altitude
70:
69:
62:
1885:
1837:
1820:
1819:
1787:
1785:
1783:
1772:
1755:
1754:
1752:
1750:
1741:. Archived from
1730:
1721:
1720:
1718:
1716:
1707:. Archived from
1696:
1687:
1677:
1668:
1667:
1662:. Archived from
1656:
1610:
1608:
1607:
1602:
1600:
1593:
1590:
1586:
1579:
1578:
1575:
1568:
1566:
1565:
1562:
1560:
1559:
1554:
1548:
1547:
1543:
1536:
1533:
1521:
1517:
1513:
1512:
1511:
1508:
1506:
1505:
1494:
1487:
1486:
1483:
1481:
1480:
1471:
1469:
1468:
1465:
1461:
1454:
1453:
1448:
1447:
1444:
1433:
1431:
1430:
1427:
1425:
1424:
1413:
1412:
1408:
1401:
1398:
1389:
1386:
1370:
1366:
1363:Rounding up 1.98
1358:
1350:
1346:
1342:
1340:
1339:
1334:
1332:
1330:
1329:
1326:
1322:
1315:
1314:
1311:
1310:
1307:
1305:
1304:
1299:
1293:
1286:
1285:
1282:
1280:
1279:
1274:
1268:
1261:
1260:
1257:
1242:
1240:
1239:
1234:
1232:
1231:
1228:
1205:
1203:
1202:
1197:
1195:
1192:
1181:
1179:
1178:
1173:
1168:
1165:
1160:
1157:
1153:
1146:
1142:
1139:
1138:
1134:
1127:
1124:
1112:
1110:
1109:
1104:
1102:
1099:
1084:
1082:
1081:
1076:
1071:
1067:
1066:
1065:
1062:
1053:
1052:
1049:
1038:
1036:
1035:
1032:
1030:
1029:
1018:
1017:
1013:
1006:
1003:
998:
995:
974:density altitude
963:
951:
949:
948:
943:
929:
927:
926:
921:
907:
905:
904:
899:
897:
894:
881:
879:
878:
873:
871:
870:
867:
865:
862:
846:
844:
843:
838:
833:
829:
828:
827:
822:
818:
817:
815:
808:
807:
804:
802:
801:
796:
790:
782:
778:
777:
773:
772:
771:
768:
766:
765:
756:
752:
731:
728:
724:
717:
716:
713:
711:
708:
678:
674:
672:
671:
666:
648:
644:
642:
641:
636:
618:
614:
612:
611:
606:
592:
584:
580:
578:
577:
572:
558:
554:
552:
551:
546:
544:
543:
540:
517:
515:
514:
509:
479:
477:
476:
471:
469:
468:
465:
450:
448:
447:
442:
424:
422:
421:
416:
414:
411:
396:
394:
393:
388:
383:
379:
378:
377:
376:
375:
367:
363:
356:
354:
346:
338:
329:
325:
323:
322:
321:
318:
312:
303:
302:
301:
298:
292:
283:
265:
260:
259:
256:
250:
245:
242:
82:density altitude
65:
58:
54:
51:
45:
27:
19:
1893:
1892:
1888:
1887:
1886:
1884:
1883:
1882:
1863:
1862:
1844:
1826:
1817:
1813:
1809:Wayback Machine
1781:
1779:
1775:
1767:
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1724:
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1712:
1698:
1697:
1690:
1678:
1671:
1658:
1657:
1653:
1649:
1617:
1598:
1597:
1570:
1552:
1551:
1519:
1518:
1498:
1473:
1457:
1439:
1438:
1434:
1417:
1416:
1390:
1376:
1375:
1368:
1364:
1356:
1348:
1344:
1318:
1297:
1272:
1252:
1247:
1246:
1223:
1218:
1217:
1186:
1185:
1115:
1114:
1093:
1092:
1057:
1044:
1043:
1039:
1022:
1021:
989:
988:
970:
961:
934:
933:
912:
911:
888:
887:
860:
855:
854:
794:
786:
758:
757:
748:
744:
743:
736:
732:
706:
701:
700:
690:
676:
657:
656:
646:
627:
626:
616:
597:
596:
590:
582:
563:
562:
556:
535:
530:
529:
500:
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460:
455:
454:
433:
432:
405:
404:
347:
339:
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236:
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199:
144:
142:Aircraft safety
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17:
12:
11:
5:
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1842:External links
1840:
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1799:
1798:, Revised 1997
1788:
1773:
1769:Air Navigation
1764:
1762:
1759:
1757:
1756:
1722:
1688:
1669:
1666:on 2016-12-23.
1650:
1648:
1645:
1644:
1643:
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1633:
1631:Density of air
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1613:
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1539:
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1516:
1504:
1500:
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1490:
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1460:
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1442:
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1423:
1419:
1407:
1404:
1396:
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1391:
1384:
1383:
1361:
1360:
1357:36,000 ft
1321:
1303:
1292:
1289:
1278:
1267:
1264:
1255:
1244:
1226:
1215:
1212:mean sea level
1183:
1171:
1163:
1152:
1149:
1133:
1130:
1122:
1086:
1085:
1074:
1070:
1060:
1056:
1047:
1042:
1028:
1024:
1012:
1009:
1001:
969:
966:
958:
957:
941:
931:
919:
909:
848:
847:
836:
832:
826:
821:
814:
811:
800:
789:
785:
764:
760:
751:
747:
742:
739:
735:
723:
720:
689:
686:
685:
684:
664:
654:
634:
624:
604:
594:
570:
560:
538:
527:
507:
497:
463:
452:
440:
430:
398:
397:
386:
382:
374:
371:
366:
362:
359:
353:
350:
345:
342:
335:
328:
316:
311:
307:
296:
291:
287:
281:
276:
273:
269:
263:
254:
248:
228:
225:
198:
195:
187:
186:
183:
160:
159:
155:
143:
140:
134:(IAS) and its
68:
67:
34:listed sources
31:
29:
22:
15:
13:
10:
9:
6:
4:
3:
2:
1890:
1879:
1876:
1874:
1871:
1870:
1868:
1859:
1856:
1854:
1851:
1849:
1846:
1845:
1841:
1835:
1831:
1830:
1824:
1815:
1814:
1810:
1806:
1803:
1800:
1797:
1793:
1789:
1778:
1774:
1770:
1766:
1765:
1760:
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1740:
1736:
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1727:
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1665:
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1655:
1652:
1646:
1642:
1639:
1637:
1634:
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1619:
1618:
1614:
1594:
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1580:
1571:
1556:
1540:
1537:
1528:
1525:
1523:
1514:
1502:
1499:
1491:
1488:
1477:
1474:
1458:
1449:
1440:
1435:
1421:
1418:
1405:
1402:
1394:
1392:
1374:
1373:
1372:
1359:) is reached.
1354:
1319:
1301:
1290:
1287:
1276:
1265:
1262:
1253:
1245:
1224:
1216:
1213:
1209:
1184:
1161:
1150:
1131:
1128:
1120:
1091:
1090:
1089:
1072:
1068:
1058:
1054:
1045:
1040:
1026:
1023:
1010:
1007:
999:
987:
986:
985:
983:
979:
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168:Quito Airport
165:
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136:true airspeed
133:
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118:
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99:
95:
92:at which the
91:
87:
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53:
41:
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35:
30:
26:
21:
20:
1828:
1791:
1780:. Retrieved
1768:
1747:. Retrieved
1743:the original
1738:
1713:. Retrieved
1709:the original
1704:
1664:the original
1654:
1636:Hot and high
1362:
1347:°C per 1,000
1087:
981:
977:
973:
971:
959:
849:
691:
486:hectopascals
399:
230:
200:
188:
164:hot and high
161:
145:
121:
106:
88:relative to
81:
79:
56:
47:
36:
683:of dry air.
615:≈ 8.3144598
227:Calculation
176:aerodynamic
172:Mexico City
158:conditions.
109:temperature
94:air density
37:may not be
1867:Categories
1761:References
1749:14 January
1715:14 January
1353:tropopause
681:molar mass
675:≈ 0.028964
488:(hPa), or
1782:9 January
1685:1047-6415
1581:−
1557:∘
1503:∘
1489:−
1478:∘
1422:∘
1395:≈
1302:∘
1288:−
1277:∘
1263:≈
1208:millibars
1162:−
1121:≈
1055:−
1027:∘
1000:≈
976:from the
799:∘
763:∘
741:−
722:145442.16
645:≈ 9.80665
619:J/mol·K,
589:(below 11
585:K/m, ISA
569:Γ
370:−
358:−
349:Γ
275:−
262:Γ
247:≈
220:free-fall
204:drop zone
197:Skydiving
50:July 2013
1805:Archived
1615:See also
980:and the
679:kg/mol,
581:= 0.0065
555:= 288.15
492:: 29.92
128:airfoils
117:humidity
86:altitude
39:reliable
1794:, U.S.
1367:°C to 2
524:kelvins
496:(inHg);
216:hypoxia
152:airfoil
84:is the
1683:
1587:
1544:
1529:1.2376
1495:
1462:
1409:
1369:
1365:
1349:
1345:
1323:
1294:
1269:
1154:
1135:
1014:
962:
791:
788:459.67
779:
753:
750:17.326
725:
677:
647:
617:
591:
583:
557:
427:meters
191:runway
1825:from
1647:Notes
1541:118.8
1406:118.8
1011:118.8
956:(°F).
825:0.235
649:m/s,
1784:2006
1751:2015
1717:2015
1681:ISSN
1584:1782
1355:(at
1320:1000
1291:1.98
1151:1013
964:ft.
884:feet
774:inHg
692:The
593:km);
526:(K);
429:(m);
124:lift
80:The
1459:500
1258:ISA
1193:QNH
1166:QNH
1063:ISA
868:NWS
714:NWS
522:in
212:QFE
208:QNH
170:or
1869::
1832:.
1737:.
1725:^
1703:.
1691:^
1672:^
1591:ft
1576:OA
1549:ft
1534:PA
1492:15
1466:ft
1455:PA
1445:OA
1414:ft
1399:PA
1387:DA
1327:ft
1316:PA
1266:15
1229:OA
1158:mb
1143:mb
1140:ft
1132:27
1100:PA
1050:OA
1019:ft
1004:PA
996:DA
984::
908:);
895:ft
863:DA
729:ft
709:DA
541:SL
518:,
480:,
466:SL
412:DA
319:SL
299:SL
257:SL
243:DA
1836:.
1786:.
1753:.
1719:.
1595:.
1572:T
1563:C
1538:+
1526:=
1515:]
1509:C
1484:C
1450:+
1441:T
1436:[
1428:C
1403:+
1308:C
1283:C
1254:T
1225:T
1214:;
1182:;
1170:)
1148:(
1129:+
1073:.
1069:)
1059:T
1046:T
1041:(
1033:C
1008:+
940:T
918:P
886:(
835:.
831:)
820:]
813:T
810:+
805:F
784:P
769:F
746:[
738:1
734:(
719:=
663:M
653:;
633:g
623:;
603:R
537:T
506:T
462:P
439:P
385:.
381:]
373:1
365:)
361:1
352:R
344:M
341:g
334:(
327:)
315:T
310:/
306:T
295:P
290:/
286:P
280:(
272:1
268:[
253:T
210:/
63:)
57:(
52:)
48:(
42:.
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