Questions tagged [boeing-737]

A short- to medium-range twinjet narrow-body airliner, originally introduced in 1968. With over 10,500 aircraft delivered and over 4500 on order, the Boeing 737 is the most popular commercial jetliner in history.

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What sort of debris has been found in 737 Max fuel tanks?

There have been numerous reports of Boeing finding "foreign object debris" in the fuel tanks of its 737 Max airliners. It's not clear what this debris is. It could range from a couple of missing ...
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Why does the KC-46 use two sensors for MCAS when the 737 Max doesn’t?

this article states The KC-46 has a two-sensor MCAS system, which “compares the two readings,” the Air Force said. I’m aware that the 737 uses two sensors and always has, but the computer reads ...
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Is the 737NG hydraulically controlled or electronically controlled?

I know that the 737NG is not fly-by-wire, but are the control surfaces controlled with hydraulic systems that transfer the input from the pilot to the control surfaces via fluid (hydraulics), or is ...
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Best Practices when removing/inspecting/mounting control surfaces?

I am looking for a better way to essentially "mount" the control surfaces from a Boeing 737-747-777-787 and MD-11's. The current process is to just remove them and strap to a table. The issues with ...
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How does MCAS communicate with other systems to know if the flaps are retracted or not?

How exactly does MCAS communicate with the flaps setting to know if the flaps have been retracted? I just noticed on the preliminary report for ET302, the flaps were set at 5 degrees. It doesn’t say ...
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What does VIB stand for in EICAS?

From what I know it’s measuring engine vibrations? What do the numbers actually mean? For example, 1.9 VIB:
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Were airworthiness certificates revoked for B737 Max?

Following up from this question - or more specifically Brian Drummond's comment on the accepted answer: Or even revoked without modification, if something new is discovered about the existing ...
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Why didn’t Boeing ramp 737NG production back up in response to the 737 MAX groundings?

The predecessor of the currently-grounded 737 MAX is the 737 Next Generation (737NG), produced from 1997 through 2019. The NG family (comprising the 737-600, -700, -800, and -900) is extremely ...
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Did the First Officer of Ethiopian Flight 302 trim in the wrong direction? [closed]

Looking at the accident report of Ethiopian Airlines Flight 302, it says the cut out switches were used. But the manual trim moved from 2.3-2.1? My reasoning for asking this is because the timeframe ...
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Does the Boeing 737 NG have “5” radar altitude callout?

So, I was watching a video of a Boeing 737 NG land, and heard the "5" callout. Is that an airline option or something? EDIT : link to video
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Is B 737 Max able to comply with certification if MCAS is off or removed? [duplicate]

Boeing 737 Max updated MCAS will probably be cutted off in case of AoA disagree. Without MCAS, the plane is no longer similar to 737 NG (stick force per g requirement). Does that mean a new ...
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If Boeing used two sensors instead of one simultaneously, wouldn’t they be in the same position today?

this article states that the original version of MCAS was suppose to rely on two sensors, One sensor will detect a high angle of attack, therefore activating MCAS The other sensor will ...
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What is this flange on the engine?

Flying home from the Denver ComiCon, on a 737, I saw an angled flange on the engine. Could you describe its purpose? Photos by CGCampbell licensed CC0
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What would be the impact of replacing the engines on the 737 MAX, not just reworking MCAS?

There has obviously been a lot of focus on the MCAS failure following from the 737 MAX crashes. However, the MCAS appears to be a compensating control for design decisions, specifically the ...
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How does a Boeing 737 look like at night from 2000 meters away? [closed]

I am asking about the current crash of a Boeing 737-800. Due to the unfortunate crash of Ukrainian 752, I am trying to figure out what can be seen from the launch pad when they decided to shoot the ...
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Why was there no thrust from the engines in the TACA Flight 110 incident?

I have just watched Mayday episode 11, season 11, "Nowhere to Land" about TACA Flight 110 incident. Most key issues of the incident are clearly explained in the episode: Why both engines turned ...
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192 views

How much power does the APU generate in a Boeing 737-300?

I have just watched Mayday episode 11, season 11, "Nowhere to Land" about TACA Flight 110 incident and I was more than surprised to learn that: APU must be turned on, APU needs about 5-10 minutes to ...
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Does the 737 MAX's engine nacelle camber affect the pitching moment?

A side view of the B737 MAX's engine nacelle shows a positive camber at the top. As nose camber of any lifting shape (wing or nacelle) generally allows more lift at higher AoA, do you think this ...
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Did Boeing need MCAS because the 737 MAX didn’t meet FAA longitudinal stability requirements, or was it to make the MAX feel like the NG?

I’m confused on this. I’ve read in multiple different places that MCAS was required due to the easier stick forces at a high angle of attack and a high G force, and because of this, the Max didn’t ...
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Will the 737 Max 10 have MCAS?

With the fuselage plugs forward of the wing, would this mean the engines are closer to CG, therefore no need for MCAS?
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Why wasn't the 737 MAX's landing gear lengthened enough to mount the engines under the wings, rather than in front of them?

The reason Boeing originally added the MCAS to the 737 MAX was to compensate for a slight pitch-up moment generated by the engine nacelles at very high angles of attack. This pitch-up moment occurred ...
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How much thrust is applied in a 737 to achieve taxi speeds?

I'd imagine not much, but maybe none? I wouldn't be surprised if the plane moves forward without brakes alone.
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Why force the nose of 737 Max down in the first place?

Can someone here explain a pretty basic question that I have had ever since this controversy came to light? I don't understand why any aircraft manufacturer, engineer, software developer, would make ...
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Why does the 737 auto-land trim up at around 400 feet RA?

From the 737NG FCOM: 400 Feet Radio Altitude The stabilizer is automatically trimmed an additional amount nose up. If the A/Ps subsequently disengage, forward control column force may be ...
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What are the correct fixes for the MAX's pitch control systems? [closed]

At this point, the ramifications of faulty data input from only one sensor into the MCAS system of the 737-MAX are well understood, having allegedly led to 346 deaths, losses of almost 10B USD for ...
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When does a Maximum Taxi Weight Restriction happen on a 737-800?

This is the first time I experienced restriction in taxi weight on B737-800. Have you experienced that before? All I know that restrictions will be from MZFW/MTOW/MLW. When does it happen?
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Why are the Boeing 737 nacelles odd shaped?

Why is a Boeing 737 NG engine not completely round in shape? It seems to be flat at the bottom and round at the top and sides. Earlier Boeing 737 versions (100 and 200) seem to have a more rounded ...
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What is the strange object on 737-800 exterior, on the aft right side?

I was unable to locate this on a "real life" picture of the aircraft, so have attached an image from my simulator. What is the function/purpose of this object on the exterior of the 738? It seems like ...
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What exactly are the “sealed” leading-edge slats in B737 short field performance aircraft?

"The 737 design enhancements allow operators to fly increased payload in and out of airports with runways less than 5,000 feet long. The design enhancements include a two-position tail skid that ...
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What turn to intercept a radial and how to tune in B737ng sim?

Forgive my very amateur questions, I have been out of flying for years now and I am getting fit to fly again after slight setback. I have an opportunity of doing some refresher flying in 737NG ...
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What is the impact of thermal Anti-Ice on descent performance?

I am just another one of the passionate flight simmers trying to understand more about Anti-ice system mechanics. I am talking about the Boeing 737-800 here if it makes a difference. What bothers me ...
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What could cause the Boeing “Pickle Fork” issues?

The Boeing 737-NG has been in the news recently regarding cracks discovered in the "pickle fork" assembly which transfers loads from the wings to the body of the aircraft. The "pickle fork" was ...
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What physical hardware does all the avionics on the B737NG run on? Some processor from the 1980s? Or some new and improved chip?

So, I am a tech guy and likes to fly (in sims) so, I was wondering what physical hardware powers all the 737NG's avionics and related systems (PFD, MFD, EICAS, GPWS etc). Is there an answer to this?
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What does “POS ITERV WAS CHGD” mean on the ACARS page of a Boeing 737?

During the whole flight, the message "POS ITERV WAS CHGD" appeared frequently on the ACARS page of the MCDU (Multipurpose Control and Display Unit). The aircraft is a Boeing 737. I cannot find any ...
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190 views

How to change 737 Max to 737 NG?

With the on going grounding of 737 Max, if some airlines want to change their 737 Max to 737 NG what modification is needed? The main change would be the engine and control system. Any other change is ...
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How much does the horizontal stabilizer on a 737 move for one unit of trim?

Inspired by this question, what exactly is the meaning of a stab trim unit? Is it exactly one degree of stabilizer movement? The 737 NG FCOMv2 (9.20.9 Flight Controls - System Description) only lists ...
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What are the checklist items for a runaway stab trim on a B737 MAX 8 and MAX 9?

This is a follow up question to this question. This question is not directly related to the MCAS system in the new B737 MAX aircraft, instead, my question is about the checklist for a runaway stab ...
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How can a runaway trim become so difficult to fight when all a pilot has to do, is “grasp and hold?” [closed]

and how can you even tell the pilots did “grasp and hold” during an investigation? Is it determined based off what they say?
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Can the 737 Max autopilot be engaged when some sensors have failed?

If some instruments on the 737 MAX 8 fail on the Captain's side and autopilot stops, can the First Officer engage autopilot (as the instruments on his side are fine)? In the ET 302 crash the Captain ...
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Why would Boeing be under review if crew-error is determined to be the cause? [closed]

The captain on Lion air's flight 610, re-trimmed the aircraft through 21 MCAS activations. The first officer, who was given control of the aircraft, got 5 more. Although it is speculated that neither ...
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Where and when would a 737-700 be taking off at an altitude of 19 kft?

Another question triggered by reading the 737 technical site; according to this section of the page on the 737's pressurisation system, the 737-700 comes with an option that allows it to safely take ...
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Do all 737NG have inerting systems?

My understanding is that Boeing 737-600/-700/-800/-900 are all 737NG. I've read before that the previous generation (737 Classic) can't be used in the USA as they don't have fuel inerting systems. ...
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Why is a 737 Original speed-restricted below 10 kft with inoperative windscreen heating?

According to this page on the 737's operational limitations, the Original 737s (737-100/-200) are limited to 250 KIAS below 10 kilofeet if the windscreen-heating system is inoperative: Anti-Ice &...
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How long is maximum time to investigate an airplane crash?

Lion Air flight 610 was crashed on 29 October 2018. It was Boeing 373 Max 8. Almost one year ago. I have not heard any news from National Transportation Safety Committee (NTSC) when they will release ...
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What are these five indicators at the front of the 737 passenger cabin?

As a passenger I noticed set of five indicators on ceiling at the front of the 737 passenger cabin. They are: red, yellow (or white), blue, white, red. Red ones seem to be coupled together (what ...
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Why couldn’t Boeing just use the stab trim system to do MCAS job?

If I’m incorrect in the question, please correct me. From what I’ve read and gathered the stab trim system essentially did the same before hand? It relies on AoA? And if so, did the computer for that ...
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Why do the 737-100's JT8Ds, and no others, have suck-in doors?

Of the various use cases of the Pratt & Whitney JT8D (the most-produced low-bypass turbofan in history, and the second-most-produced turbofan of any description1), those installed on the 737-100 ...
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How many turns of a 737 trim wheel equal 2.5 degrees stabilizer deflection?

After the well known crashes I looked at the question of stabilizer trimming. In case of trim runaway the pilot is supposed to "grasp and hold" the wheel manually steering the stabilizer. Hence my ...
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Would a 737 pilot use flaps in nose dive?

Since flaps help lift the plane, would they deploy flaps if the plane was nosediving? And what would they do if the back pressure was too much? I know speed increases lift, but can full throttle make ...

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