I recently decided to purchase the PMDG Boeing 737-700 to complete my collection. However, I have noticed a handful of things that I have rarely encountered in any of the other versions.

• When I entered the FMS calculated figure for the ZFW in the 737-700 BBJ1 (96.6), it stated that it was INVALID. I noticed that I could manually enter 96.7, and it worked fine. This may be as simple as a rounding error somewhere, but it does not happen with any of the other versions of the 737 (and I mean all of them).

• I have noticed that rotation of the 737-700 sometimes abruptly stops on take off. I thought that this was a bug, but the most recent example of this was followed by a conversation between the pilot and the cabin crew about a possible tail strike. Now, I have had one of these in the 737-900, and since then I have been more careful when rotating this version. However, I did not expect it to happen with the 737-700 (with its significantly shorter fuselage). Maybe it is just easier to rotate the 700, and I need to be more careful? It is worth noting that I have never encountered this problem with the 600.

• I noticed a constantly flashing "A" left of the speed indicator on the MCP when on final approach in the 737-700 BDSF. I am aware that this is an "underspeed warning" for the aircraft's current weight and flap configuration. However, my speed was Vref+5 (as calculated by the FMS), so I would have thought that it should be fine. I am quite prepared to be taught otherwise by the real world 737 pilots with respect to this one!

I fly all of my PMDG aircraft with no passengers and no cargo, so I am aware that I am at the outer edge of the flight model envelope. Nevertheless, I have not encountered the first and last points above with any of the other versions of the 737. I have seen the flashing "A" with the 600, but it always disappears when the aircraft has stabilised.

Just a hunch: Have you checked whether your -700, unlike your -600, is set up to use kilograms instead of pounds?

Regarding the "pause" during rotation: This is something the 737s are known for; it's caused by the horizontal stabilizer entering ground effect. I would assume the effect is stronger the longer the fuselage is, which might explain why you haven't seen the effect on the -600.

1 hour ago, weaklink said:

Just a hunch: Have you checked whether your -700, unlike your -600, is set up to use kilograms instead of pounds?

Regarding the "pause" during rotation: This is something the 737s are known for; it's caused by the horizontal stabilizer entering ground effect. I would assume the effect is stronger the longer the fuselage is, which might explain why you haven't seen the effect on the -600.

Everything is set to pounds. Anyway, a PMDG beta tester has replicated the issue, so it looks like a bug. As for the rotation, I am pretty sure that it was due to tail strikes. I have been more careful today with rotation of the 700, and it performed smoothly each time. I have not noticed the effect in the 800 or 900 either, although I may have missed it that one time that I suffered a tail strike in the 900.

Edited Saturday at 02:04 PM4 days by Christopher Low

4 hours ago, Christopher Low said:

I fly all of my PMDG aircraft with no passengers and no cargo

Why would you do that?? You just make it much harder on your since those aircraft are designed with a certain weight in mind ad if you fly them empty handling becomes much harder.

6 minutes ago, Farlis said:

Why would you do that?? You just make it much harder on your since those aircraft are designed with a certain weight in mind ad if you fly them empty handling becomes much harder.

This is a simulator. I can fly my planes in any way that I like. Handling has never been a problem in the fourteen years that I have been flying the PMDG 737 like this.

26 minutes ago, Farlis said:

Why would you do that??

Same reason pilots like the 757? 😎

Wheeeeeeeeeee

31 minutes ago, Farlis said:

You just make it much harder on your since those aircraft are designed with a certain weight in mind ad if you fly them empty handling becomes much harder.

One person's "making it hard on yourself" is just another person's "setting myself a challenge"?

And from what I hear, real-world pilots typically enjoy the opportunity to do an empty ferry flight...

46 minutes ago, Farlis said:

Why would you do that?? You just make it much harder on your since those aircraft are designed with a certain weight in mind ad if you fly them empty handling becomes much harder.

I'm afraid that is not an entirely correct statement.

Why would we know this? Because airlines routinely conduct ferry (repositioning) flights with little or no payload, moving aircraft between maintenance bases or operational stations. These flights provide a direct comparison between a virtually empty aircraft and one operating near its maximum certified weight.

From a flight control perspective, the difference is surprisingly small—almost negligible. The force required to move the controls is governed primarily by dynamic pressure, which is a function of airspeed and air density, not aircraft weight. At a given airspeed, the aerodynamic hinge moments acting on the control surfaces remain essentially the same regardless of how much payload is on board.

On aircraft such as the Boeing 737, the primary flight controls are hydraulically powered and incorporate an artificial feel system (control feel and centering unit). This system intentionally provides the pilot with consistent control forces that vary mainly with airspeed and hydraulic feel pressure, rather than with aircraft weight. As a result, the controls remain linear, smooth, and predictable whether the aircraft is nearly empty or operating close to maximum takeoff weight.

For that reason, I have never encountered evidence supporting the statement that "these aircraft are designed with a certain weight in mind, and if you fly them empty the handling becomes much harder." That simply does not match either the aircraft's engineering or my operational experience.

What does change is the aircraft's response, not the control force. An empty airplane has less mass and therefore less inertia. Consequently, it accelerates more quickly, decelerates more readily, rotates with less resistance, climbs better, and generally responds more briskly to the same control inputs. Likewise, lower weight reduces wing loading, improving climb performance and reducing stall speed. During repositioning flights, even with reduced takeoff thrust, the airplane accelerates noticeably faster and delivers significantly better overall performance.

In other words, the controls themselves do not become "harder" or fundamentally different because the airplane is empty. What changes is the aircraft's inertia and performance, while the artificial feel system ensures that the pilot experiences nearly the same control feel throughout the certified weight envelope.

6 hours ago, Christopher Low said:

I noticed a constantly flashing "A" left of the speed indicator on the MCP when on final approach in the 737-700 BDSF. I am aware that this is an "underspeed warning" for the aircraft's current weight and flap configuration. However, my speed was Vref+5 (as calculated by the FMS), so I would have thought that it should be fine.

In normal circumstances, the only time you'd see the alpha floor warning (the 'A' next to the MCP speed) at VREF+5 is if you're at that speed but haven't set landing flaps for the calculated speed. Perhaps you were still at flaps 15?

Edited Saturday at 03:43 PM4 days by JYW

I was at Flaps 25 at 140 knots, and the calculated final approach speed was 121+5=126 knots. I dropped to Flaps 30 at 130 knots.

3 hours ago, Farlis said:

Why would you do that?? You just make it much harder on your since those aircraft are designed with a certain weight in mind ad if you fly them empty handling becomes much harder.

Nope.

light planes are easy planes.

7 hours ago, Christopher Low said:

I recently decided to purchase the PMDG Boeing 737-700 to complete my collection. However, I have noticed a handful of things that I have rarely encountered in any of the other versions.

• When I entered the FMS calculated figure for the ZFW in the 737-700 BBJ1 (96.6), it stated that it was INVALID. I noticed that I could manually enter 96.7, and it worked fine. This may be as simple as a rounding error somewhere, but it does not happen with any of the other versions of the 737 (and I mean all of them).

• I have noticed that rotation of the 737-700 sometimes abruptly stops on take off. I thought that this was a bug, but the most recent example of this was followed by a conversation between the pilot and the cabin crew about a possible tail strike. Now, I have had one of these in the 737-900, and since then I have been more careful when rotating this version. However, I did not expect it to happen with the 737-700 (with its significantly shorter fuselage). Maybe it is just easier to rotate the 700, and I need to be more careful? It is worth noting that I have never encountered this problem with the 600.

• I noticed a constantly flashing "A" left of the speed indicator on the MCP when on final approach in the 737-700 BDSF. I am aware that this is an "underspeed warning" for the aircraft's current weight and flap configuration. However, my speed was Vref+5 (as calculated by the FMS), so I would have thought that it should be fine. I am quite prepared to be taught otherwise by the real world 737 pilots with respect to this one!

I fly all of my PMDG aircraft with no passengers and no cargo, so I am aware that I am at the outer edge of the flight model envelope. Nevertheless, I have not encountered the first and last points above with any of the other versions of the 737. I have seen the flashing "A" with the 600, but it always disappears when the aircraft has stabilised.

Weird that you’re not getting this in any of the others.

One thing that kinda sticks out to me is you’re flying the BBJ.

It can carry significantly more fuel, etc,

Perhaps a quick run in the pax variant to see if the conditions continue? I would expect that’s the most commonly flown PMDG variant with the least bugs, etc

I fly every single version of the PMDG 737 one after the other (1x600, 4x700s, 5x800s, and 4x900s), and the 737-700 BBJ1 is the only one that exhibits this bug. Manually entering 96.7 is the very easy work around for now, but as the PMDG beta tester stated on the PMDG forum, "double clicking the LSK L3 line should always work, so it needs to be fixed".

We used to position empty 747-400s between airports only 30 miles apart. We imposed a minimum fuel load of 24T to keep the forward fuel pumps covered in the initial climb out, the deck angle was over 20 degrees and we’d be approaching a height of 2,000ft passing the end of the runway!

5 hours ago, jon b said:

We used to position empty 747-400s between airports only 30 miles apart. We imposed a minimum fuel load of 24T to keep the forward fuel pumps covered in the initial climb out, the deck angle was over 20 degrees and we’d be approaching a height of 2,000ft passing the end of the runway!

It’s amazing to watch a Heavy do an airshow routine. We’re goin ballistic!!! 😁

6 hours ago, jon b said:

We used to position empty 747-400s between airports only 30 miles apart. We imposed a minimum fuel load of 24T to keep the forward fuel pumps covered in the initial climb out, the deck angle was over 20 degrees and we’d be approaching a height of 2,000ft passing the end of the runway!

Indeed, I loved KJFK to KEWR on 773, 744, and 748; we used a minimum fuel of 30T due to operational limitations. The kicker was waiting for tower-to-tower clearance to take off JFK 31L at 3,000 FT visual to rwy 29 in EWR. Speed was limited to 180 KTS; all that was no more than an 8-minute direct flight to CRI and line up for 29. Such is life. Even TO2 with assumed the temperature would give, as you mentioned, an over-20-degree deck angle to stay on profile.

Edited Sunday at 01:11 AM3 days by LRBS