To descend and set up an approach in a Boeing 737, we work backwards from the runway: calculate top of descent, brief the arrival, load and verify the approach, then manage speed, altitude and configuration so the aircraft is fully stabilised by 1,000 feet in IMC or 500 feet in VMC.
When should we start descending in the 737?
The basic rule most sim pilots use is the 3:1 rule. For every 1,000 feet you need to lose, allow about 3 nautical miles. If you are at 35,000 feet and need to be at 3,000 feet for the approach, that is 32,000 feet to lose, so roughly 96 NM before the target point.
Then add extra distance for slowing down. A 737 can lose height quite neatly, but if you stay fast for too long you will arrive high and fast at the approach. As a rough planning aid, add another 10 to 15 NM if you need to decelerate from cruise to approach speeds.
So if your calculation says 96 NM, your practical top of descent may be more like 105 to 115 NM out depending on wind, aircraft weight, STAR restrictions and how aggressively you plan to slow down.
Quick mental rules that work well in the sim
| Task | Rule of thumb |
|---|---|
| Lose altitude | 3 NM per 1,000 feet |
| 3 degree descent rate | Groundspeed x 5 |
| Extra distance for slowing | Add 10-15 NM if needed |
| Stable final target | Configured, on speed, on path by 1,000 ft IMC or 500 ft VMC |
That descent-rate rule is handy on approach. If your groundspeed is 160 knots, a 3 degree path is about 800 fpm. At 140 knots, it is about 700 fpm.
How do we set up the 737 for the approach?
The exact button presses vary between a simple default aircraft and a detailed add-on, but the workflow is the same. We want the navigation, altitude constraints, speeds and landing configuration sorted early, not at the last minute.
- Review the arrival and approach. Confirm the runway, STAR or transition, final approach course, decision altitude or minimums, missed approach altitude and likely landing flap setting. If there is strong wind or a short runway, think about that now rather than on short final.
- Load and verify the approach. In an FMC-equipped 737, insert the arrival and approach, then check every waypoint, altitude restriction and runway selection against the chart or briefing material you are using. Never assume the FMC got it right.
- Tune what needs tuning. For an ILS, set the correct frequency and front course if your 737 variant requires it. Some add-ons auto-tune from the FMC; some do not. Always verify the identifier and course before relying on the localiser.
- Set the missed approach altitude. Put the go-around altitude in the MCP before you intercept the glideslope or final path. This is a common thing sim pilots forget, and it matters if you have to go around.
- Plan top of descent and start down early enough. Use VNAV if the route and restrictions are entered properly. If not, use LVL CHG, V/S or a manual descent and monitor the path yourself.
- Manage speed before managing flap. A 737 rewards being ahead of the aircraft. Slow in stages, meet speed restrictions, and do not wait until the final approach to get rid of excess energy.
- Briefly configure for landing. Set autobrake as required, arm the speedbrake before landing, check landing data or VREF, and decide your flap setting. In most sim flying that will usually be flap 30 unless conditions suggest otherwise.
- Intercept the final approach properly. Localiser from below or on level trend is ideal; glideslope from below is essential. Do not dive onto a glideslope from above and expect a tidy result.
- Be fully stabilised early. By 1,000 feet in IMC or 500 feet in VMC, the aircraft should be on the correct path, in landing configuration, thrust stable and speed close to target. If it is not, go around.
VNAV, LVL CHG or V/S: which should we use?
This depends on how detailed your 737 is and how well the route is built. In a study-level aircraft, VNAV can handle descent and many approach constraints very well, but only if the FMC data is correct. In simpler aircraft, manual modes are often more predictable.
| Mode | Best use | Main watch-out |
|---|---|---|
| VNAV | Managed descent with route constraints | Bad FMC data leads to bad descent planning |
| LVL CHG | Strong, simple descents while holding selected speed | Can become steep if you leave it late |
| V/S | Fine control and path corrections | Easy to get high/low or fast/slow if you stop monitoring |
| APP | Capturing ILS localiser and glideslope | Should be established correctly before capture |
If you are still learning, a very dependable combination is this: descend with LVL CHG or VNAV, slow in stages, then capture the ILS with APP once you are correctly positioned. If you use V/S, keep a constant eye on speed, because the aircraft will happily trade energy in ways you did not intend.
Typical 737 speed and configuration flow
The exact numbers depend on variant, weight and airline procedure, so always use your aircraft's own speed bugs, FMC data and flap placard limits. Still, there is a very standard pattern most sim pilots can follow.
| Phase | Typical target | What we are doing |
|---|---|---|
| Initial descent | High-speed cruise descent | Start down on profile, stay ahead of restrictions |
| Below 10,000 ft | 250 kt or local limit | Reduce speed and prepare for approach setup |
| Approach preparation | 210-220 kt | Begin flap extension as needed |
| Base/intercept | 180 kt-ish | Gear can come down, more flap, capture final path |
| Final approach | VREF + additive, often +5 | Landing flap set, thrust stable, checklist complete |
A common training flow is to be around 180 knots when intercepting the localiser, then gear down and further flap as the aircraft settles onto the glideslope. The exact point varies with traffic, weather and how your sim aircraft models drag.
Common flap and drag habits
- Use flap in stages; do not dump full flap too early unless you need drag badly.
- Use the speedbrake mainly when clean or lightly configured, not as a crutch once fully established with landing flap.
- Get the gear down early enough if you are still too fast. The gear is excellent drag.
- Do not chase every knot. Aim for a stable trend, not constant thrust and pitch sawing.
What is a good descent rate on the approach?
For a normal 3 degree glidepath, use groundspeed x 5 as your starting point. That gives you a close enough vertical speed for most sim flying:
- 140 kt groundspeed: about 700 fpm
- 150 kt groundspeed: about 750 fpm
- 160 kt groundspeed: about 800 fpm
- 180 kt groundspeed: about 900 fpm
If there is a strong headwind, the groundspeed will be lower, so the descent rate required for the same glidepath is also lower. That catches a lot of people out when they fly the same indicated speed but see different glidepath behaviour in windy conditions.
How do we avoid ending up high and fast?
This is the classic 737 approach problem in sims. The fix is nearly always earlier planning, not more last-second control input.
- Start down a little earlier if there is a tailwind.
- Slow down before the final approach rather than on it.
- Use speedbrake promptly if you see the profile getting away from you.
- Respect published restrictions on the STAR and transition.
- Do not try to capture the glideslope from above.
If you are still high at the final approach fix, the safest answer is usually to break off the approach and set up again. In a simulator it is tempting to salvage everything. In a real 737, unstable approaches are not something we would normalise.
ILS setup in a 737: what should we check before final?
Before the aircraft turns onto final, we want the radios and guidance to make sense. That means the runway agrees with the FMC, the ILS frequency and course are correct if manually set, the localiser is alive when expected, and the missed approach altitude is set.
Then arm the approach mode at a sensible point, usually when you are established for capture rather than miles too early. If you are flying manually, use the raw data as a cross-check even if the FMC map looks perfect.
On many 737 add-ons, an autoland or dual-channel setup requires extra steps and very specific conditions. If you are not explicitly training for that, treat the approach as a normal single-channel ILS and focus on flying a stable path.
What counts as a stable approach in the sim?
A stable approach is not just “roughly lined up”. By the gate height, the aircraft should be:
- On the correct lateral path
- On the correct vertical path
- At a stable target speed
- In landing configuration
- With only small changes in thrust and pitch needed
- With checklist items complete
A widely used benchmark is stable by 1,000 feet above airfield level in IMC or 500 feet in VMC. If you are still chasing speed, flap, localiser or glideslope at that point, the disciplined answer is a go-around.
If it all goes wrong, go around early
The best 737 sim pilots are not the ones who rescue every bad setup. They are the ones who recognise a bad setup early and go around before it becomes messy.
If you are high, fast, badly offset, or not configured in time, add thrust, pitch to the go-around attitude, follow the missed approach, clean up on schedule and try again. It is better flying, and it builds habits that transfer properly from one simulator to another.