Cruising pitch and passengers?

[blueaircraft]

Generally speaking, at what degree does a cruise pitch become uncomfortable for passengers? The pitch can be both positive and negative.

Regards,
Andrew.

[Tom/CalClassic]

Personally I don’t have a limit, under normal airliner flying conditions. I feel just fine when a plane is climbing or descending, which is usually at an angle far greater than most cruising attitudes.

One good reason to minimize the cruising attitude is to maximize the efficiency of the flight.

[mrcapitalism]

I'd say the initial takeoff of a modern jet airliner, which climbs hard to acceleration altitude, is unbearable for walking in the cabin. That's almost always more than 10 degrees nose up.

[Tom/CalClassic]

Yeah, I wasn’t including initial takeoff. Only after gear and flaps are up, and climb speed has been attained.

[Defender]

With one exception the real world manuals I have make no comment on cabin comfort and pitch so it doesn't seem to be important. The exception is SAS's DC-7C manual which has this notation at certain "high and heavy" sections of the performance tables but never below 22,000'.

"(these) speeds are below minimum speeds for comfortable flight characteristics"

Presumably excessive positive pitch but interesting that it mentions comfort rather than aerodynamic efficiency. Interesting too is that there is no such restriction in these tables for light weights at short haul low altitudes when there would be similar levels of negative pitch.

Bill

[Tom/CalClassic]

I have noticed that too, and I was wondering if the manual meant comfortable for the passengers, or comfortable for the plane?

[blueaircraft]

Nov 1, 2023 11:51:10 GMT -5 mrcapitalism said:

I'd say the initial takeoff of a modern jet airliner, which climbs hard to acceleration altitude, is unbearable for walking in the cabin. That's almost always more than 10 degrees nose up.

Yes that is true! But I'm wondering about the pitch during cruise. For example, most jetliners fly a cruise pitch at around 1 or 2 degrees up. But how would passengers feel about a cruise pitch that is 1 or 2 degrees down? A zero degree pitch? That's the question.

Regards
Andrew

[blueaircraft]

Nov 1, 2023 9:22:19 GMT -5 Tom/CalClassic said:

Personally I don’t have a limit, under normal airliner flying conditions. I feel just fine when a plane is climbing or descending, which is usually at an angle far greater than most cruising attitudes.

One good reason to minimize the cruising attitude is to maximize the efficiency of the flight.

Thanks Tom! So you're saying that you're okay with a cruise pitch of say, 1 or 2 degrees up OR 1 or 2 degrees down when not step climbing or climbing or descending?

Regards
Andrew

[blueaircraft]

Nov 1, 2023 14:43:52 GMT -5 Defender said:

With one exception the real world manuals I have make no comment on cabin comfort and pitch so it doesn't seem to be important. The exception is SAS's DC-7C manual which has this notation at certain "high and heavy" sections of the performance tables but never below 22,000'.

"(these) speeds are below minimum speeds for comfortable flight characteristics"

Presumably excessive positive pitch but interesting that it mentions comfort rather than aerodynamic efficiency. Interesting too is that there is no such restriction in these tables for light weights at short haul low altitudes when there would be similar levels of negative pitch.

Bill

It can still make a difference... but perhaps not 

Regards
Andrew

[mrcapitalism]

Nov 1, 2023 21:05:42 GMT -5 blueaircraft said:

But I'm wondering about the pitch during cruise.

There's a very big discussion on this forum about cruise pitch, and it makes zero reference to passenger comfort. I only mentioned takeoff because it's the only situation in which I can imagine the pitch of the cabin being anything that can be described as 'unbearable.' Meaning, no other situation would qualify in my opinion. It's usually a little more than 1-2, probably 2-5. The wings are surprisingly symmetrical with little incidence.

But how would passengers feel about a cruise pitch that is 1 or 2 degrees down? A zero degree pitch? That's the question.

I personally don't think they'd care too much. Just so long as walking isn't too difficult for weaker passengers, or could cause a problem with cabin service carts.

But again, excessive cabin (fuselage) pitch indicates other more pressing problems..

I also interpret "comfortable flight characteristics" describing the flight controls, not the opinions in the cabin. I'm thinking aircraft stability. My first flight in the Team Connie L1049 I climbed right up to FL250 for a transcon and proceeded to blissfully dutch roll half way across the United States

[Defender]

Hi Tom,

I should have looked further in the SAS manual. Comfortable does indeed relate to aerodynamics, the 1.05 V l/d speeds, and it's set out in page 4.2.3.

Bill

PS - I understand that this 1.05 Vl/d max weight/speed line shows the IAS for a given weight 5% above the point of maximum aerodynamic and so fuel efficiency. So no benefit is operating above this limit? No idea what this means for pitch!

[Tom/CalClassic]

I would doubt there is any advantage of flying faster than that, unless you need to meet scheduled times. Sometimes flights were scheduled faster than that for competitive reasons. I assume you would be flying nose down in that case.

[Defender]

Sorry Tom, my post was a bit misleading as the V l/d speeds are minimums not maximums and in most respects relevant only to long range cruise.

The Douglas Aircraft Corporation manual which I think you have explains it rather better and includes this comment,

"At airspeeds below Vl/d the airplane speed power stabilization becomes extremely difficult, flying conditions are less comfortable and maneuvering potential is reduced"

Andrew, apologies if all this doesn't address your question, but low speeds will generally result in nose up. Perhaps that minimum speed limit means that the DC-7C's published operating settings would rarely result in significant positive pitch.

Bill

[Tom/CalClassic]

I think we sort of talked past each other. I am assuming that the 1.05 Vl/d speed is the most aerodynamic speed, I did realize that Vl/d is a minimum.

[mrcapitalism]

I assume "V l/d" means "Airspeed for L/D Max"?
interesting how SAS even wants a 5% buffer over that (we're allowed L/D MAX).

Tangentially related. None of these propliners have any sort of stall warning/stall protection devices, do they?