{"id":2451,"date":"2025-10-19T11:39:00","date_gmt":"2025-10-19T09:39:00","guid":{"rendered":"https:\/\/acriv.org\/WP\/?page_id=2451"},"modified":"2025-10-19T11:39:00","modified_gmt":"2025-10-19T09:39:00","slug":"vfr-tips","status":"publish","type":"page","link":"https:\/\/acriv.org\/WP\/vfr-tips\/","title":{"rendered":"VFR : TIPS"},"content":{"rendered":"\n<h1 class=\"wp-block-heading has-vivid-red-color has-luminous-vivid-amber-background-color has-text-color has-background has-link-color wp-elements-6c9b91b9d42168ad097b59a10a6357cd\">\ud83e\udded FICHE CALCUL MENTAL \u2013 NAVIGATION VFR (CAPS, D\u00c9RIVE, VENT, COMPAS)<\/h1>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">1\ufe0f\u20e3 Cha\u00eene compl\u00e8te de navigation (de la carte au compas)<\/h2>\n\n\n\n<p>On part toujours de la <strong>Route vraie (RV)<\/strong> (celle mesur\u00e9e sur la carte) pour arriver au <strong>Cap compas (CC)<\/strong> (celui affich\u00e9 dans l\u2019avion).<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\ud83d\udd39 Sch\u00e9ma de principe :<\/h3>\n\n\n\n<p><strong>RV \u2192 (\u00b1 d\u00e9rive) \u2192 CV \u2192 (\u00b1 d\u00e9clinaison magn\u00e9tique) \u2192 CM \u2192 (\u00b1 d\u00e9viation compas) \u2192 CC<\/strong><\/p>\n\n\n\n<figure class=\"wp-block-table\"><table><thead><tr><th>\u00c9tape<\/th><th>\u00c9l\u00e9ment<\/th><th>Symbole<\/th><th>Correction<\/th><th>R\u00e9sultat<\/th><\/tr><\/thead><tbody><tr><td>1<\/td><td>Route vraie<\/td><td>RV<\/td><td>\u00b1 d\u00e9rive (\u0394)<\/td><td>Cap vrai (CV)<\/td><\/tr><tr><td>2<\/td><td>Cap vrai<\/td><td>CV<\/td><td>\u00b1 d\u00e9clinaison (Var)<\/td><td>Cap magn\u00e9tique (CM)<\/td><\/tr><tr><td>3<\/td><td>Cap magn\u00e9tique<\/td><td>CM<\/td><td>\u00b1 d\u00e9viation (Dev)<\/td><td>Cap compas (CC)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">2\ufe0f\u20e3 D\u00e9rive due au vent<\/h2>\n\n\n\n<p>Le <strong>vent<\/strong> fait d\u00e9vier ton avion de sa route. Tu dois <strong>corriger<\/strong> en ajoutant ou retirant un angle de d\u00e9rive (\u0394).<\/p>\n\n\n\n<h3 class=\"wp-block-heading\">\ud83d\udd38 Formule approximative (r\u00e8gle du vent traversier)<\/h3>\n\n\n\n<p><code>\u0394 = (vent_traversier \/ vitesse_sol) \u00d7 60 \/ distance_NM \u00d7 distance_corrig\u00e9e<\/code> \u2192 trop lourd mentalement.<br>\ud83d\udc49 Simplifions avec la <strong>r\u00e8gle des 60<\/strong>.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">\ud83d\udd39 R\u00e8gle des 60 simplifi\u00e9e (\u00e0 conna\u00eetre absolument) :<\/h3>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>\u201c60 NM parcourus \u2192 1\u00b0 = 1 NM de d\u00e9calage lat\u00e9ral.\u201d<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p>Autrement dit :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Si au bout de 60 NM tu es d\u00e9cal\u00e9 de 1 NM, tu avais 1\u00b0 de d\u00e9rive.<\/li>\n\n\n\n<li>Si tu veux corriger 2 NM de d\u00e9rive sur 30 NM :<br>\u0394 = (2 \/ 30) \u00d7 60 = 4\u00b0 de d\u00e9rive.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">\ud83d\udd39 Calcul mental rapide de la d\u00e9rive avec le vent :<\/h3>\n\n\n\n<p>Formule approch\u00e9e (pour vent \u2264 30 kt) :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><code>\u0394 \u2248 (Vvent \u00d7 sin(\u03b1)) \/ Vair \u00d7 60 \/ 60<\/code><br>\u2192 simplifi\u00e9 : <code>\u0394 \u2248 (Vvent \u00d7 sin(\u03b1)) \/ Vair \u00d7 57<\/code> mais on arrondit en pratique.<\/p>\n<\/blockquote>\n\n\n\n<p>R\u00e8gle pratique :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>D\u00e9rive (\u00b0) \u2248 (Vent traversier \/ Vitesse avion) \u00d7 60 \/ 60 \u2192 simplifi\u00e9 \u00e0<br><code>\u0394 \u2248 (Vent traversier \/ TAS) \u00d7 60 \/ 60 \u2248 (Vent traversier \/ TAS) \u00d7 57<\/code> \u2248 <code>(Vent traversier \/ TAS) \u00d7 60<\/code>.<\/p>\n<\/blockquote>\n\n\n\n<p>\ud83d\udc49 Exemple : vent traversier 15 kt, avion 100 kt \u2192<br>\u0394 \u2248 (15 \/ 100) \u00d7 60 \/ 60 = 9\u00b0 (approximation simple : 15% de 60 \u2248 9\u00b0).<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h3 class=\"wp-block-heading\">\ud83d\udd39 R\u00e8gle du vent (pour tracer au CRP ou mentalement)<\/h3>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Calcule la <strong>composante de vent de face \/ dos<\/strong> : <code>Vent_face = Vvent \u00d7 cos(\u03b1)<\/code><\/li>\n\n\n\n<li>Calcule la <strong>composante traversi\u00e8re<\/strong> : <code>Vent_trav = Vvent \u00d7 sin(\u03b1)<\/code><\/li>\n\n\n\n<li>D\u00e9rive : <code>\u0394 = arcsin(Vent_trav \/ TAS)<\/code><br>(mentalement, tu arrondis avec la r\u00e8gle ci-dessus)<\/li>\n\n\n\n<li>Corrige la vitesse sol : <code>GS = TAS \u00b1 Vent_face<\/code><\/li>\n<\/ol>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">3\ufe0f\u20e3 Application du signe de la d\u00e9rive<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Vent venant <strong>de la droite<\/strong> \u2192 tu <strong>pousses ton nez \u00e0 droite<\/strong> \u2192 d\u00e9rive <strong>positive<\/strong>.<\/li>\n\n\n\n<li>Vent venant <strong>de la gauche<\/strong> \u2192 tu <strong>pousses ton nez \u00e0 gauche<\/strong> \u2192 d\u00e9rive <strong>n\u00e9gative<\/strong>.<\/li>\n<\/ul>\n\n\n\n<p>\ud83d\udca1 R\u00e8gle mn\u00e9motechnique :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>\u201cVent de droite \u2192 Cap \u00e0 droite.\u201d<\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">4\ufe0f\u20e3 D\u00e9clinaison magn\u00e9tique (variation)<\/h2>\n\n\n\n<p>C\u2019est la diff\u00e9rence entre le <strong>Nord vrai (Nv)<\/strong> et le <strong>Nord magn\u00e9tique (Nm)<\/strong>.<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Ouest (W)<\/strong> : Nord magn\u00e9tique <strong>\u00e0 l\u2019Ouest<\/strong> du Nord vrai<br>\u2192 Le <strong>cap magn\u00e9tique est inf\u00e9rieur<\/strong> au cap vrai<br>\u2192 <strong>Soustraire<\/strong> la d\u00e9clinaison<br>\ud83d\udc49 \u201cVar W \u2014 West is less\u201d<\/li>\n\n\n\n<li><strong>Est (E)<\/strong> : Nord magn\u00e9tique <strong>\u00e0 l\u2019Est<\/strong> du Nord vrai<br>\u2192 Le <strong>cap magn\u00e9tique est sup\u00e9rieur<\/strong> au cap vrai<br>\u2192 <strong>Ajouter<\/strong> la d\u00e9clinaison<br>\ud83d\udc49 \u201cVar E \u2014 East is least\u201d (version anglophone invers\u00e9e pour m\u00e9moire : <em>East = Add<\/em>)<\/li>\n<\/ul>\n\n\n\n<p><strong>Formule :<\/strong><\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>CM = CV \u00b1 Var<br>(Var E + \/ Var W \u2013)<\/p>\n<\/blockquote>\n\n\n\n<p><strong>Exemple :<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>CV = 180\u00b0, Var = 2\u00b0W \u2192 CM = 180 \u2212 2 = <strong>178\u00b0<\/strong><\/li>\n\n\n\n<li>CV = 270\u00b0, Var = 3\u00b0E \u2192 CM = 270 + 3 = <strong>273\u00b0<\/strong><\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">5\ufe0f\u20e3 D\u00e9viation compas<\/h2>\n\n\n\n<p>Erreur propre \u00e0 ton compas due au champ magn\u00e9tique de l\u2019avion (donn\u00e9e par la <strong>courbe de d\u00e9viation<\/strong> dans le carnet de route).<\/p>\n\n\n\n<p><strong>Formule :<\/strong><\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p>CC = CM \u00b1 Dev<br>(Dev E + \/ Dev W \u2013)<\/p>\n<\/blockquote>\n\n\n\n<p>Exemple :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>CM = 178\u00b0, Dev = 2\u00b0E \u2192 CC = 178 + 2 = <strong>180\u00b0<\/strong><\/li>\n\n\n\n<li>CM = 090\u00b0, Dev = 1\u00b0W \u2192 CC = 090 \u2212 1 = <strong>089\u00b0<\/strong><\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">6\ufe0f\u20e3 Cha\u00eene compl\u00e8te d\u2019exemple (r\u00e9sum\u00e9 pratique)<\/h2>\n\n\n\n<p><strong>Donn\u00e9e :<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>RV = 105\u00b0<\/li>\n\n\n\n<li>Vent du 030\u00b0 \/ 20 kt<\/li>\n\n\n\n<li>TAS = 100 kt<\/li>\n\n\n\n<li>Var = 3\u00b0W<\/li>\n\n\n\n<li>Dev = 2\u00b0E<\/li>\n<\/ul>\n\n\n\n<h3 class=\"wp-block-heading\">\u00c9tapes :<\/h3>\n\n\n\n<p>1\ufe0f\u20e3 Angle vent = 105 \u2212 30 = 75\u00b0 \u2192 sin(75\u00b0) \u2248 0.97<br>\u2192 Vent traversier \u2248 0.97\u00d720 \u2248 19 kt \u2192 d\u00e9rive \u2248 (19\/100)\u00d760\/60 \u2248 <strong>11\u00b0 droite<\/strong><br>\u2192 CV = 105 + 11 = <strong>116\u00b0<\/strong><\/p>\n\n\n\n<p>2\ufe0f\u20e3 Corrige variation 3\u00b0W (West is less) \u2192 CM = 116 \u2212 3 = <strong>113\u00b0<\/strong><\/p>\n\n\n\n<p>3\ufe0f\u20e3 Corrige d\u00e9viation 2\u00b0E \u2192 CC = 113 + 2 = <strong>115\u00b0<\/strong><\/p>\n\n\n\n<p>\u2705 <strong>Cap compas \u00e0 afficher : 115\u00b0<\/strong><\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">7\ufe0f\u20e3 Calcul mental de la vitesse sol (GS)<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>GS = TAS \u00b1 Vent_face<br>\u2192 Vent_face = Vvent \u00d7 cos(\u03b1)<\/li>\n<\/ul>\n\n\n\n<p><strong>Exemple :<\/strong><br>M\u00eame cas : vent du 030\/20, route 105 \u2192 angle 75\u00b0 \u2192 cos(75\u00b0)=0.26<br>Vent_face = 0.26\u00d720=5 kt<br>\u2192 GS = 100 \u2212 5 = <strong>95 kt<\/strong> (vent 5 kt de face).<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">8\ufe0f\u20e3 R\u00e8gle des 1-60 pour corrections en route<\/h2>\n\n\n\n<p>Si tu constates un \u00e9cart lat\u00e9ral en vol :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>Pour corriger :<\/strong><br>Corrige ton cap de <code>(\u00e9cart lat\u00e9ral en NM \/ distance parcourue) \u00d7 60<\/code> degr\u00e9s.<\/p>\n<\/blockquote>\n\n\n\n<p><strong>Exemple :<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Apr\u00e8s 30 NM, tu es 2 NM \u00e0 gauche de ta route.<br>\u2192 Correction = (2 \/ 30) \u00d7 60 = 4\u00b0.<br>Tu corriges ton cap de <strong>4\u00b0 vers la droite<\/strong> pendant la m\u00eame distance pour revenir sur la route.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">9\ufe0f\u20e3 R\u00e9sum\u00e9 mental : \u00ab R\u2192R\u2192R \u00bb<\/h2>\n\n\n\n<p>Quand tu appliques les corrections :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>RV \u2192 + d\u00e9rive \u2192 CV \u2192 \u00b1 variation \u2192 CM \u2192 \u00b1 d\u00e9viation \u2192 CC<\/strong><\/p>\n<\/blockquote>\n\n\n\n<p>et inversement pour revenir :<\/p>\n\n\n\n<blockquote class=\"wp-block-quote is-layout-flow wp-block-quote-is-layout-flow\">\n<p><strong>CC \u2192 \u2213 d\u00e9viation \u2192 CM \u2192 \u2213 variation \u2192 CV \u2192 \u2213 d\u00e9rive \u2192 RV<\/strong><\/p>\n<\/blockquote>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\ud83d\udd1f Table de d\u00e9rive rapide (r\u00e8gle du vent)<\/h2>\n\n\n\n<p><em>(pour un avion \u00e0 100 kt, d\u00e9rive approximative selon vent traversier)<\/em><\/p>\n\n\n\n<figure class=\"wp-block-table\"><table><thead><tr><th>Vent traversier (kt)<\/th><th>D\u00e9rive (\u00b0)<\/th><\/tr><\/thead><tbody><tr><td>5<\/td><td>3\u00b0<\/td><\/tr><tr><td>10<\/td><td>6\u00b0<\/td><\/tr><tr><td>15<\/td><td>9\u00b0<\/td><\/tr><tr><td>20<\/td><td>12\u00b0<\/td><\/tr><tr><td>25<\/td><td>15\u00b0<\/td><\/tr><tr><td>30<\/td><td>18\u00b0<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<p>Pour d\u2019autres vitesses :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>80 kt \u2192 d\u00e9rive plus forte (\u00d7100\/80 \u2192 +25%)<\/li>\n\n\n\n<li>120 kt \u2192 d\u00e9rive plus faible (\u00d7100\/120 \u2192 \u221217%)<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">\u2699\ufe0f R\u00e9sum\u00e9 final : les 6 formules cl\u00e9s \u00e0 conna\u00eetre par c\u0153ur<\/h2>\n\n\n\n<figure class=\"wp-block-table\"><table><thead><tr><th>Calcul<\/th><th>Formule mentale<\/th><th>Exemple<\/th><\/tr><\/thead><tbody><tr><td><strong>1. D\u00e9rive<\/strong><\/td><td>(Vent traversier \/ TAS) \u00d7 60 \/ 60 \u2248 (Vent traversier \/ TAS) \u00d7 57<\/td><td>15 kt \/ 100 kt \u2248 9\u00b0<\/td><\/tr><tr><td><strong>2. Cap vrai<\/strong><\/td><td>CV = RV \u00b1 d\u00e9rive<\/td><td>+ si vent de droite<\/td><\/tr><tr><td><strong>3. Cap magn\u00e9tique<\/strong><\/td><td>CM = CV \u00b1 Var (E + \/ W \u2013)<\/td><td>Var 3W \u2192 \u20133\u00b0<\/td><\/tr><tr><td><strong>4. Cap compas<\/strong><\/td><td>CC = CM \u00b1 Dev (E + \/ W \u2013)<\/td><td>Dev 2E \u2192 +2\u00b0<\/td><\/tr><tr><td><strong>5. GS<\/strong><\/td><td>TAS \u00b1 Vent_face (Vvent \u00d7 cos \u03b1)<\/td><td>vent face 10 kt \u2192 GS = TAS\u221210<\/td><\/tr><tr><td><strong>6. Correction de route<\/strong><\/td><td>(\u00e9cart lat\u00e9ral \/ distance) \u00d7 60<\/td><td>2 NM\/30 NM = 4\u00b0<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h1 class=\"wp-block-heading has-vivid-red-color has-luminous-vivid-amber-background-color has-text-color has-background has-link-color wp-elements-c83f22d89981a8c0b6c5bc24b35abff1\">Fiche : formules et m\u00e9thodes de calcul mental VFR<\/h1>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">1) Principes de base &amp; conversions utiles<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>1 NM = <strong>6076 ft<\/strong> (approxim\u00e9 souvent \u00e0 6080 ft)<\/li>\n\n\n\n<li>1 kt = <strong>1 NM \/ h<\/strong><\/li>\n\n\n\n<li>1 m = <strong>3.2808 ft<\/strong><\/li>\n\n\n\n<li>1 hPa \u2248 <strong>27 ft<\/strong> d\u2019altitude (r\u00e8gle pratique utilis\u00e9e en Europe ; certains utilisent 30 ft\/hPa comme approximation)<\/li>\n<\/ul>\n\n\n\n<p>Conversions rapides :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>ft \u2192 m : \u00f7 <strong>3.2808<\/strong><\/li>\n\n\n\n<li>m \u2192 ft : \u00d7 <strong>3.2808<\/strong><\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">2) Pente en degr\u00e9s \u21c4 ft par NM \u21c4 pourcentage<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>ft par NM<\/strong> pour une pente donn\u00e9e (formule pr\u00e9cise) :<br><code>ft_per_NM = tan(deg \u00d7 \u03c0\/180) \u00d7 6076<\/code><\/li>\n<\/ul>\n\n\n\n<p>R\u00e8gles pratiques (arrondies, tr\u00e8s utilis\u00e9es par les pilotes) :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>1\u00b0 \u2248 107 ft \/ NM<\/strong> (r\u00e8gle approximative : 100 ft\/NM utilis\u00e9e parfois)<\/li>\n\n\n\n<li><strong>3\u00b0 \u2248 319 ft \/ NM<\/strong> (r\u00e8gle pratique: \u2248 300 ft\/NM)<\/li>\n\n\n\n<li><strong>5\u00b0 \u2248 531 ft \/ NM<\/strong><\/li>\n\n\n\n<li><strong>Degr\u00e9s \u2192 pourcentage<\/strong> : <code>pourc = tan(deg) \u00d7 100<\/code><br>R\u00e8gle rapide : <code>pourc \u2248 deg \u00d7 1.745<\/code> (car tan(1\u00b0)\u00d7100 \u2248 1.745%)<\/li>\n\n\n\n<li><strong>Pourcentage \u2192 degr\u00e9s<\/strong> : <code>deg = arctan(pourc\/100) \u00d7 180\/\u03c0<\/code><\/li>\n<\/ul>\n\n\n\n<p><strong>Exemples :<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>3\u00b0 \u2192 ft\/NM \u2248 3 \u00d7 107 = <strong>321 ft\/NM<\/strong> (plus pr\u00e9cis\u00e9ment ~318.6 ft\/NM)<\/li>\n\n\n\n<li>2\u00b0 \u2192 pourc \u2248 2 \u00d7 1.745 = <strong>3.49%<\/strong><\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">3) Taux de descente (ft\/min) \u00e0 maintenir<\/h2>\n\n\n\n<p>Formule :<br><code>fpm = (ft_per_NM \u00d7 GS_kt) \/ 60<\/code><br>( GS_kt = ground speed en kt ; on divise par 60 car GS kt = NM\/h )<\/p>\n\n\n\n<p><strong>Exemples :<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Pente 3\u00b0 \u2192 ft\/NM \u2248 <strong>318.6<\/strong>. \u00c0 GS = 120 kt :<br><code>fpm = 318.6 \u00d7 120 \/ 60 = 318.6 \u00d7 2 = 637.2 \u2248 640 fpm<\/code><\/li>\n\n\n\n<li>R\u00e8gle pratique souvent utilis\u00e9e :<br><code>fpm \u2248 300 \u00d7 GS \/ 60 = 5 \u00d7 GS<\/code> (pour une approche \u22483\u00b0 arrondie).<br>\u2192 \u00e0 100 kt \u2192 <code>fpm \u2248 500 ft\/min<\/code>.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">4) Distance (NM) \u00e0 commencer la descente<\/h2>\n\n\n\n<p>Formules :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>distance_NM = altitude_to_lose_ft \/ ft_per_NM<\/code><\/li>\n\n\n\n<li>ou, en minutes : <code>time_min = altitude_to_lose_ft \/ fpm<\/code> puis <code>distance_NM = time_min \u00d7 GS \/ 60<\/code><\/li>\n<\/ul>\n\n\n\n<p><strong>Exemples :<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Tu es \u00e0 5500 ft et tu veux descendre au niveau de l\u2019a\u00e9rodrome (0 ft) sur une approche 3\u00b0 (~319 ft\/NM) :<br><code>distance = 5500 \/ 319 \u2248 17.24 NM<\/code> \u2192 commencer la descente \u2248 <strong>17.2 NM<\/strong> avant l\u2019a\u00e9rodrome.<\/li>\n\n\n\n<li>Si tu pr\u00e9f\u00e8res utiliser fpm : \u00e0 GS 120 kt et fpm 640 : <code>time_min = 5500 \/ 640 \u2248 8.59 min<\/code> \u2192 distance = <code>8.59 \u00d7 120 \/ 60 = 8.59 \u00d7 2 = 17.18 NM<\/code>.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">5) Plan de descente rapide \u2014 <strong>m\u00e9thode pratique<\/strong><\/h2>\n\n\n\n<ol class=\"wp-block-list\">\n<li>Calcule l\u2019altitude \u00e0 perdre (ex : FL055 \u2192 QNH = 0 \u2192 perdre 5500 ft).<\/li>\n\n\n\n<li>Choisis pente (3\u00b0 par d\u00e9faut pour approche) \u2192 ft\/NM \u2248 320.<\/li>\n\n\n\n<li><code>distance_NM = altitude \/ 320<\/code> \u2192 arrondir.<\/li>\n\n\n\n<li>Calcule fpm si besoin : <code>fpm = 320 \u00d7 GS \/ 60<\/code>.<\/li>\n<\/ol>\n\n\n\n<p>Exemple compact : altitude 2500 ft, GS 100 kt, pente 3\u00b0 :<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>distance = 2500 \/ 320 \u2248 <strong>7.8 NM<\/strong> \u2192 commencer ~8 NM avant.<\/li>\n\n\n\n<li>fpm = 320 \u00d7 100 \/ 60 = 320 \u00d7 1.6667 \u2248 <strong>533 ft\/min<\/strong>.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">6) Vitesse vraie (TAS) approximative \u00e0 partir de IAS<\/h2>\n\n\n\n<p>R\u00e8gle pratique : <strong>TAS augmente ~2% par 1000 ft<\/strong> d\u2019altitude.<br>Formule : <code>TAS \u2248 IAS \u00d7 (1 + 0.02 \u00d7 altitude_1000ft)<\/code><\/p>\n\n\n\n<p><strong>Exemple :<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>IAS = 100 kt \u00e0 5000 ft \u2192 alt_1000 = 5 \u2192 TAS \u2248 100 \u00d7 (1 + 0.02\u00d75) = 100 \u00d7 1.10 = <strong>110 kt<\/strong>.<\/li>\n<\/ul>\n\n\n\n<p>Remarque : pour plus de pr\u00e9cision, utiliser E6B ou calculateur, surtout aux hautes altitudes.<\/p>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">7) Altitude pression &amp; altitude densit\u00e9 (formules utiles)<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Pressure altitude (ft)<\/strong> \u2248 <code>elevation_ft + (1013.25 - QNH_hPa) \u00d7 27<\/code><br>(arrondi : \u00d727 ft\/hPa)<\/li>\n\n\n\n<li><strong>Density altitude (ft)<\/strong> (r\u00e8gle approximative) :<br><code>density_alt \u2248 pressure_alt + 120 \u00d7 (OAT_C - ISA_temp_at_alt_C)<\/code><\/li>\n<\/ul>\n\n\n\n<p>O\u00f9 : <code>ISA_temp_at_alt_C \u2248 15 - 2 \u00d7 (alt_ft\/1000)<\/code> (lapse rate ~2\u00b0C\/1000 ft)<\/p>\n\n\n\n<p><strong>Exemple :<\/strong><\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li>QNH = 1000 hPa, niveau mer (elevation 0) : pressure_alt \u2248 <code>(1013.25 - 1000) \u00d7 27 = 13.25 \u00d7 27 \u2248 357.75 ft<\/code> \u2192 <strong>~358 ft<\/strong>.<\/li>\n\n\n\n<li>\u00c0 PA = 2000 ft, OAT = 30\u00b0C \u2192 ISA temp \u2248 <code>15 - 2\u00d72 = 11\u00b0C<\/code>. Temp diff = 30 &#8211; 11 = 19\u00b0C \u2192 density_alt \u2248 <code>2000 + 120\u00d719 = 2000 + 2280 = 4280 ft<\/code>.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">8) Correction altim\u00e8tre \/ erreurs li\u00e9es \u00e0 la temp\u00e9rature (r\u00e8gle pratique)<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Air froid = altitude vraie plus basse que l\u2019indiqu\u00e9e<\/strong> \u2192 il faut <strong>ajouter<\/strong> une correction pour obtenir la hauteur vraie au-dessus du sol.<\/li>\n\n\n\n<li>Pas de formule simple et fiable \u00e0 la main pour toutes les situations \u2014 utiliser tableau de correction (CAA\/FAA) ou demander au contr\u00f4le.<\/li>\n\n\n\n<li>R\u00e8gle pratique (approx) : pour approches en air tr\u00e8s froid, la diff\u00e9rence peut devenir significative (quelques dizaines \u00e0 centaines de ft selon \u0394T et altitude). Toujours appliquer correction officielle si fournie.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">9) Calculs relatifs \u00e0 la pression et QNH (rapide)<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>Pour estimer l\u2019effet d\u2019une variation de 1 hPa sur l\u2019altitude : \u2248 <strong>27 ft<\/strong>.<\/li>\n\n\n\n<li>Si ton altim\u00e8tre indique 3000 ft avec QNH X et que QNH augmente de 10 hPa, la r\u00e9f\u00e9rence change \u2248 <strong>270 ft<\/strong>.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">10) Autres rappels mentaux pratiques<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>R\u00e8gle des 3 minutes<\/strong> (petits a\u00e9ronefs, r\u00e8gle non officielle) : pour une mont\u00e9e\/descente \u201cdouce\u201d ~1000 ft\/min on estime temps \u2248 altitude\/1000 \u00d7 1 min (trop approximatif). Pr\u00e9f\u00e8re la m\u00e9thode ft\/NM + GS.<\/li>\n\n\n\n<li><strong>Distance d\u2019anticipation pour circuits<\/strong> : r\u00e8gle commune = <strong>2\u20133 NM<\/strong> pour rentrer dans le circuit final selon a\u00e9ronef et vitesse (adapter).<\/li>\n\n\n\n<li><strong>Arrondis pratiques<\/strong> : arrondir les ft\/NM \u00e0 100, la distance \u00e0 0.5 NM, le fpm \u00e0 10 ft\/min pour garder le calcul mental rapide.<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">11) Tableau r\u00e9capitulatif (formules cl\u00e9s)<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><code>ft_per_NM \u2248 6076 \u00d7 tan(deg)<\/code><\/li>\n\n\n\n<li><code>fpm = ft_per_NM \u00d7 GS \/ 60<\/code><\/li>\n\n\n\n<li><code>distance_NM = altitude_to_lose \/ ft_per_NM<\/code><\/li>\n\n\n\n<li><code>TAS \u2248 IAS \u00d7 (1 + 0.02 \u00d7 altitude_1000ft)<\/code><\/li>\n\n\n\n<li><code>pressure_alt \u2248 elevation + (1013.25 \u2212 QNH) \u00d7 27<\/code><\/li>\n\n\n\n<li><code>density_alt \u2248 pressure_alt + 120 \u00d7 (OAT \u2212 ISA_temp_at_alt)<\/code><\/li>\n\n\n\n<li><code>deg \u2192 % : % \u2248 deg \u00d7 1.745<\/code><\/li>\n\n\n\n<li><code>1 hPa \u2248 27 ft<\/code> (approx.)<\/li>\n<\/ul>\n\n\n\n<hr class=\"wp-block-separator has-alpha-channel-opacity\"\/>\n\n\n\n<h2 class=\"wp-block-heading\">12) Exemples rapides pr\u00eats \u00e0 l\u2019emploi<\/h2>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Je dois descendre de 3600 ft, GS = 90 kt, pente 3\u00b0<\/strong> :\n<ul class=\"wp-block-list\">\n<li>ft\/NM \u2248 319 \u2192 distance = 3600 \/ 319 \u2248 <strong>11.28 NM<\/strong> \u2192 commencer ~<strong>11.3 NM<\/strong> avant.<\/li>\n\n\n\n<li>fpm = 319 \u00d7 90 \/ 60 = 319 \u00d7 1.5 = <strong>478.5 \u2248 480 fpm<\/strong>.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>IAS = 85 kt \u00e0 4000 ft \u2192 TAS ?<\/strong>\n<ul class=\"wp-block-list\">\n<li>alt_1000 = 4 \u2192 TAS \u2248 85 \u00d7 (1 + 0.02\u00d74) = 85 \u00d7 1.08 = <strong>91.8 kt<\/strong> \u2248 <strong>92 kt<\/strong>.<\/li>\n<\/ul>\n<\/li>\n\n\n\n<li><strong>QNH = 995 hPa, altitude indiqu\u00e9e 1500 ft (terrain sea-level)<\/strong> \u2192 pressure alt \u2248 (1013.25 \u2212 995)\u00d727 \u2248 18.25\u00d727 \u2248 492.75 ft \u2192 \u2248 <strong>493 ft<\/strong> (si tu veux la PA depuis le niveau de la mer).<\/li>\n<\/ol>\n","protected":false},"excerpt":{"rendered":"<p>\ud83e\udded FICHE CALCUL MENTAL \u2013 NAVIGATION VFR (CAPS, D\u00c9RIVE, VENT, COMPAS) 1\ufe0f\u20e3 Cha\u00eene compl\u00e8te de navigation (de la carte au compas) On part toujours de la Route vraie (RV) (celle mesur\u00e9e sur la carte) pour arriver au Cap compas (CC) (celui affich\u00e9 dans l\u2019avion). \ud83d\udd39 Sch\u00e9ma de principe : RV \u2192 (\u00b1 d\u00e9rive) \u2192 CV \u2192 (\u00b1 d\u00e9clinaison magn\u00e9tique) \u2192<\/p>\n<p><a class=\"more-link\" href=\"https:\/\/acriv.org\/WP\/vfr-tips\/\">Read More<\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-2451","page","type-page","status-publish","hentry"],"jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/acriv.org\/WP\/wp-json\/wp\/v2\/pages\/2451","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/acriv.org\/WP\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"https:\/\/acriv.org\/WP\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"https:\/\/acriv.org\/WP\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/acriv.org\/WP\/wp-json\/wp\/v2\/comments?post=2451"}],"version-history":[{"count":1,"href":"https:\/\/acriv.org\/WP\/wp-json\/wp\/v2\/pages\/2451\/revisions"}],"predecessor-version":[{"id":2452,"href":"https:\/\/acriv.org\/WP\/wp-json\/wp\/v2\/pages\/2451\/revisions\/2452"}],"wp:attachment":[{"href":"https:\/\/acriv.org\/WP\/wp-json\/wp\/v2\/media?parent=2451"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}