Flying Inverted in 737

[KriVa 307]

I must have missed those. My bad, carry on :rolleyes:

[Great Ozzie 101]

 

I don't see why it is not possible... I mean yes the wings could get way overstressed, and the negative g's installe aren't fun at all but it isn't unheard of or impossible. They do it in fighter jets and acrobatics aircraft, why not in a 737??

 

"Fighter jets" are designed / built with much higher structural  G limits than (most) civilian types.   What a civilian type is rated for (i.e. "limit maneuvering load factors")  is going to depend on the Category of Airworthiness Standards.

 

I say "most" civilian types as there are examples of some extremely stout airframes.  One would be the Extra 300L... it's G-Load Limit is +/- 10gs.  If you know anything at all about g loading and the effects on structures / the human body... those are very impressive numbers.

 

A typical trainer e.g. your Piper Warrior can have certification limits of +3.8g for the "Normal" Category and +4.4g for "Utility" Category ops (Airworthiness Certification regs currently require the Negative Load Limit to be 0.4 times the positive limit for Normal & Utility Categories).  What Category you are flying in the Warrior is based on Weight and C.G. and there is a chart provided in the POH to determine the Category.

 

Ok... talking about a Transport Category here.  Currently...  Minimum (not less than) is +2.5g and -1.0g (there is an exception where maneuvering load factors can be lower... in "practice" you can see lower values sometimes for the "landing configuration").

 

Been quite some time since I have done a Barrel Roll but I can certainly tell you this... it is a very low positive g maneuver... probably half (if done correctly) than what you would experience in a Loop (Inside Loop, that is).

 

So a test pilot like Tex Johnston (c'mon guys... it is with a "t") who knew precisely what he was doing, could perform a maneuver such as Barrel Roll w/o concern of overstressing the airframe.  Lest anyone think otherwise, by no means am I diminishing how spectacular that feat was.  :im Not Worthy:

 

Btw... go to Wiki and you will see it was actually the 707 prototype (for decades I thought it was the 707)... the B367-80.  A little anecdotal nugget in there about the 777... something I will let you find and enjoy yourself.

 

Found this too on youtube (not sure why he called it a "chandelle").

 

[Captain Kevin 586]

FedEx 705.

[Great Ozzie 101]

 

707 barrel roll did not go "inverted" at all

 

Then what did you mean by your "inverted"?

 

Who cares about g loading... inverted is inverted...

[Fabo 213]

 

Then what did you mean by your "inverted"?
 
Who cares about g loading... inverted is inverted...

 

It is all about the G-loading when you compare Tex Johnstons barrel roll with a minute of inverted flight in Flight. Which is what I originally replied to.

[g_precentralis 191]

Concorde also went inverted during a testflight but fighter jets and aerobatic planes are designed for this kind of flying while commercial airliners are not. 

The same as 707, that was barrel roll with positive g load.

 

The next question is can engine work properly in inverted flight? I remember some engines cannot do that, there is limited time of inverted flight (for example 20 seconds).

[DylanC 181]

 

 

"Fighter jets" are designed / built with much higher structural  G limits than (most) civilian types.   What a civilian type is rated for (i.e. "limit maneuvering load factors")  is going to depend on the Category of Airworthiness Standards.

 

I say "most" civilian types as there are examples of some extremely stout airframes.  One would be the Extra 300L... it's G-Load Limit is +/- 10gs.  If you know anything at all about g loading and the effects on structures / the human body... those are very impressive numbers.

 

A typical trainer e.g. your Piper Warrior can have certification limits of +3.8g for the "Normal" Category and +4.4g for "Utility" Category ops (Airworthiness Certification regs currently require the Negative Load Limit to be 0.4 times the positive limit for Normal & Utility Categories).  What Category you are flying in the Warrior is based on Weight and C.G. and there is a chart provided in the POH to determine the Category.

 

Ok... talking about a Transport Category here.  Currently...  Minimum (not less than) is +2.5g and -1.0g (there is an exception where maneuvering load factors can be lower... in "practice" you can see lower values sometimes for the "landing configuration").

 

Been quite some time since I have done a Barrel Roll but I can certainly tell you this... it is a very low positive g maneuver... probably half (if done correctly) than what you would experience in a Loop (Inside Loop, that is).

 

So a test pilot like Tex Johnston (c'mon guys... it is with a "t") who knew precisely what he was doing, could perform a maneuver such as Barrel Roll w/o concern of overstressing the airframe.  Lest anyone think otherwise, by no means am I diminishing how spectacular that feat was.  :im Not Worthy:

 

Btw... go to Wiki and you will see it was actually the 707 prototype (for decades I thought it was the 707)... the B367-80.  A little anecdotal nugget in there about the 777... something I will let you find and enjoy yourself.

 

Found this too on youtube (not sure why he called it a "chandelle").

 

 

LOL that's pretty funny!

 

"Boeing Chief Test Pilot John Cashman stated that just before he piloted the maiden flight of the Boeing 777 on June 12, 1994, his last instructions from then-Boeing President Phil Condit were "No rolls."^[12]"

 

 

[FlyingAxx 2]

Besides the fuel supply I'm wondering whether the way the engines are mounted would allow such a maneuver. Static forces are quite different and I could imagine that the nacelles could fall towards the wings even if the whole assemby should be designed to withstand rough conditions in flight.

[tf51d 284]

 

707 barrel roll did not go "inverted" at all, barrel rolls are low positive g maneuvers, if you were blindfolded in an aircraft you would not even know it did a barrel roll. I have done them, this is how it is.

 

Of course a Barrel Roll is an inverted maneuver, but as Paul says it's only for a second. Just because it isn't a negative G maneuver doesn't mean you aren't inverted. The centrifugal force of the roll keeps it positive G. I've done them a couple of times too!

 

[Fabo 213]

If you guys stopped repeating yourself and looked at me putting the "inverted" parts in quotes and looked at what I replied to...

 

It does not matter that barrel roll goes inverted for a second, or two or ten, as it does not go "inverted" the same way a sustained inverted flight goes, that is, inversion of the gravitational apparent relative pull.

(gravitational pull, of course, stays the same = towards the earth center)

(apparent relative pull is normally downwards towards the floor of the aircraft, same as in barrel roll, however it gets inverted in sustained inverted flight and some other maneuvers such as outside loop)

[Airbusman330 300]

 

The next question is can engine work properly in inverted flight? I remember some engines cannot do that, there is limited time of inverted flight (for example 20 seconds).

 

It depends on some engines but I would think that as long as the fuel and oil pumps are working there would be no problems. On the same topic the German BF-109 was able to handle negative g's better than the Spitfire or Mustang because it had a fuel injected engine while its rivals used carburetors and the Diamler Benz V-12 it used was inverted as well. 

[Great Ozzie 101]

 

I would think that as long as the fuel and oil pumps are working there would be no problems.

 

Well I'd imagine the question is will the pumps / sumps be able to draw from the tanks... this would include hydraulics too.

 

Think of Bob Hoover pouring tea into a glass while rolling the plane (I get a kick out of that everytime I watch it   :lol:  ).

 

 

 

as it does not go "inverted" the same way a sustained inverted flight goes, that is, inversion of the gravitational apparent relative pull.

 

Look Peter,

 

Took me a few minutes thinking about this... finally I realized...

 

If you want to talk about sustained inverted flight... don't use quotes... it is too ambiguous (why the confusion with a number of us).  If you mean that, just say "inverted flight".  Just using the word inverted is not going to cut it, however bracketed, for what it appears you really mean (i.e. sustained inverted flight).

 

Best,

-Rob

[hopskip 253]

 Sustained inverted flight with negative G loading for a period of more than 30 seconds is quite different from a barrel roll which transits through an inverted attitude with a positive G load. 

   

 The Alaskan aircraft that did this (very very loosley what the "Flight" movie incident was inspired by) was an MD80 which has fuselage-mounted engines on the back of the aircraft. How this compares to a 737 with engines mounted under the wings on pylons might be a factor, both with centre of gravity, structural integrity of the mounts, fuel feed to the engines etc. 

   

 The angle of incidence of the wing of an airliner is usually designed to have a 'fairly flat' fuselage 'floor' angle in level flight. Sustaining inverted flight will require that the nose be lifted higher to attain the same angle of attack. Also due to the wing design of airliners having a distinct camber, a higher angle of attack may be required when inverted. This will put the nose higher (in the blue) to maintain level flight when inverted when compared to "right side up" wings level = higher drag = more thrust to maintain level flight inverted. 

   

 It should be possible to remain inside -1.5 G and maybe even -1.1G with a steady hand so G stress shouldn't be a major factor. 

   

 "Getting" from wings level to inverted may be a bit tougher, but "barrel rolling" into inverted is of course possible, so you should be able to maintain positive G till established in the attitude you want to maintain for inverted flight.  

   

 Given that all works, I don't see much of an issue, certainly no "wings falling off" the plane and sustained inverted flight should work fine till the engines stop from fuel starvation. 

   

 Unfortunatley the Alaskan MD80 had a mechanical issue of it's elevator trim being locked full forward (past the full forward actually due to mechanical damage). Even before they went inverted, they had lost bits off their elevator (ie the trim tabs) due to a high-speed dive that approached and/or may have exceeded Mach 1.0.  The plane was heavily damaged even before they tried the trick of going inverted ("Push the blue side up") to get the nose up. Unfortunatley the crew of Alaska Airlines 261 didn't manage to save their aircraft. 

[flightwatch 68]

Yes but whether the longside of the wing in on bottom or top the air is still glowing the same way ( I think I might be wrong though). Therefore the aircraft can still keep lift. How do you think acrobatic aircraft do it? Remy Mermelstein 777-300 FS Pilot

Not to go off topic here but...

 

You are a very trusting person to display your full name, phone number, private email address, and city of residence on a public forum.

 

Back on topic:

 

You guys are over complicating things here. Sure a 737 can fly inverted...as can any other plane out there. Yes the engines could still operate in an inverted position. They don't know that they are upside down. As long as airflow into the engine is not disrupted, you would not notice a difference. Fuel flow would only be disrupted if performing high AoA, high speed (acceleration) maneuvers. Flying inverted would only produce -1g...which is nowhere near the acceleration required to not only overcome the tank pumps, but the EDP's as well. Certainly you would overstress the airframe long before you came close to starving the pumps.

 

The movie "Flight" is not realistic by any standards. It is actually laughable (and I did) at points. It is purely for entertainment, and shouldn't be analyzed with any hint of realism whatsoever.

[flyerguy7773 6]

@ flightwatch:

 

I have been warned many times about this. So far I have not gotten any unwanted emails, calls, requests or anything from anybody. As long as it stays that way I don't see what harm it is doing. If I do however begin to receive unwanted emails, calls or mail I will without hesitation take that information off my profile.

 

Thanks for pointing it out though

 

 

 

Remy Mermelstein

777-300 FS Pilot