12/17/2023 0 Comments Lpv lnav vnav![]() The use of Baro-VNAV as an approach type in the question is not very precise. How the missed approach point is determined is different for different types of approaches, but by definition, each approach procedure has a missed approach point. For a non vertically guided procedure, this is at a fix or a specified location along the final approach course. Managing your descent profile and making sure you break out of the soup is better than having to go missed and try the approach all over again.MISSED APPROACH POINT− A point prescribed in each instrument approach procedure at which a missed approach procedure shall be executed if the required visual reference does not exist.įor a vertically guided procedure, this is at the point on the GS where the aircraft reaches the DA. A constant glide path will lighten your workload, reduce your chance of error, and make your passengers more comfortable during the descent.īut if the clouds are near your DA, the MDA is probably the way to go. If the DA minimums will easily get you out of the clouds, following the glide path is almost always the best choice. But if you're at an airport with LNAV/VNAV and LNAV only, you have a choice to make. ![]() If you're a WAAS capable airplane, and there are LPV minimums, that's probably going to be your best route. The next time you see an approach with MDA minimums lower than DA minimums, take a minute to think about what your best choice is going to be. If the ceilings were lower than that, you probably would want to opt for the LNAV only approach, which gets you quite a bit lower. That would give you a little over 200 feet of room between you and the clouds when you reach DA. To give yourself some breathing room on the approach, you would probably want at least 1,500 foot ceilings to shoot the LNAV/VNAV approach. That's a difference of 392 feet, which is quite a bit when the ceilings are low. On the Harrisburg approach, the LNAV/VNAV approach will get you down to 1,264 feet above touchdown, and the LNAV will get you down to 872 feet above touchdown. Where are the ceilings at, and will the LNAV/VNAV approach get you under them? On an approach like this, your decision is really going to come down to the weather. That makes the approach more prone to error. You need to keep track of your step down altitudes, and manage your power settings as you transition from level flight to descents through your step down fixes. Once you're configured for your descent, it only takes minor changes to maintain your glide path.Īs for a non-precision approach, you have a lot more workload to deal with. And on top of that, you don't have to make as many power changes as you would on a "dive-and-drive" approach. When you fly an approach on a glide path, you have a continuous vertical path to follow. First off, using vertical guidance on an approach is almost always the best idea. So with all of that in mind, it brings you back to the original question, which descent minimums should you choose? The LNAV, or the LNAV/VNAV? If the MDA needs to be raised, they do it in 20 foot increments.īoldmethod What Minimums Should You Choose? ![]() But, there are several factors that can cause the MDA to be higher. So at a minimum, the LNAV MDA on an approach is at least 250 feet above the highest obstacle in your path. Then, they add 250 feet to that line for the LNAV Required Obstacle Clearance (ROC). For LNAV (lateral navigation) approaches, the FAA looks at the obstacle heights along the approach path, and draws a straight line called the Obstacle Clearance Surface (OCS). For the purposes of this article, we won't go into LPV approaches - we'll stick to LNAV/VNAV, and LNAV only approaches.įirst, let's look at approaches with no vertical guidance. There's a lot that goes into calculating the minimum altitudes for an approach, but there are a few general rules that all of them follow. You would assume that approaches with vertical guidance will get you lower than non-precision approaches, but that's not always the case. View the full Harrisburg GPS RWY 13 Approach ![]()
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