I was on a Ryanair flight this morning that seemed to perform an incredibly aggressive takeoff from London Stansted on a 737-8. Takeoff was fairly fast, but the climb was the steepest I ever encountered.
For context, we were taking off from runway 22, with wind 34 kt from the South/Southwest gusting 51 kt
Your flight took off during a storm. During a storm, the wind speed close to the surface of the earth is much lower than the wind speed a bit higher up. This variation of wind speed over a short vertical distance is called wind shear. The aircraft is taking off into the wind, so during the initial climb the headwind increases. Increasing headwind during climb does miracles to the climb rate.
Suppose you want to climb from sea level to 2000 feet while increasing the true airspeed from 140 to 160 knots (70 m/s to 80 m/s). In steady wind conditions that means the aircraft needs to accelerate 20 knots during that climb, which consumes part of the energy available from the engines.
But if there is a windshear and the headwind is increasing by 30 knots during that climb (not unreasonable in stormy conditions), the ground speed will reduce by 10 knots. Instead of needing to add kinetic energy, the aircraft needs to reduce it by converting it into potential energy (altitude). This means more energy is available for climbing and thus the climb rate is higher.
The wind reports from the airport at the time of take-off showed a wind of 29 knots (39 knots gusts), almost straight down the runway.
If you look at the wind profile this morning (I could not access yesterday's data anymore) you see that the wind increases from 20 kts at the surface to 51 knots at 3000 ft. That's a lot of free airspeed the aircraft gets during climb!
source: screenshot from windy.com
source: screenshot from windy.com
In addition, the effect of a stormy headwind is that the ground speed is relatively low. This makes the climb much steeper than in the no-wind condition.
Looking a bit closer at the raw data from FR24, the aircraft took off at 131 knots groundspeed (the first airborne report is 25 ft above the runway). 6 seconds after the first airborne ADS-B report, the altitude had increased by 525 ft. Even if we conservatively assume it took 7 seconds to climb to 500 ft (round-off errors), it requires a vertical acceleration over 1.6 g to achieve that. That must have felt very aggressive!
The first 2000 ft of climb took only 25 seconds, an average of 4800 ft per minute. The ground speed reduced to 119 knots by the time the aircraft had climbed 2800 ft, 37 seconds after take-off.
After that, the aircraft had climbed through most of the boundary layer of the earth and the windshear reduced. The rest of the climb was fairly typical.
It was not only your perception; by all means it was an impressive take-off performance for a B738
Sometimes a departing airplane will receive or be offered an accelerated climb profile from ATC which gets it up and out of the published approach and departure patterns quickly. If the pilot elects to take the profile, the resulting climb will be unusual, and spectacular.
I was on a Rockwell SabreLiner departing from San Jose, Ca in a very lightly-loaded condition some years ago when the pilot was offered this, and he took it- and warned us about how steeply we would be climbing. I was in one of the rearward-facing seats and looking backwards out the window next to me I was treated to a stunning view of downtown San Jose below us while basically hanging from my seat belt during our climbout.
It was fun.
It appears that it took the pilot about 15 mins to climb from near sea level to FL370. That's a climb rate of about 2500 feet/min, which is a pretty modest climb rate for a jet. If you're looking for fast climb rates in a transport, check out Lear 35s. If given an unrestricted climb to cruise altitude, they will often do 5000+ feet/min!
A bit more elaborated answer gathered from my comments above: First of all- what do you mean by aggressive- Shaky? fast? high pitched?
If the headwind is stable- it changes the Ground speed at which the plane rotates, making it lower. After that, the aircraft climbs at the same pitch angle as always, once it transitioned to the stage of acceleration from V2. What does change a lot is the rate of climb per distance, nor per time. The situation is different if it is gusty- then the scenario is that it's all very bumpy, and planes do trade a bit of speed for pitch due to the logic of the aircraft flight algorithm- constant thrust, changing pitch. It will be elaborated further down the answer.
If it's unstable at low alt, maybe they maintained a high pitch, low speed, flaps down climb to clear the turbulent air (they just maintained a lower speed all the way out of the boundary layer). Finally, maybe they performed a full thrust take off- which is sometimes performed when wind shear is predicted, resulting in a very steep pitch after take off for such a light plane (1-hour flight).
If the wind changes and adds additional 30 knots of headwind in an instance- and stays there- meaning another stable mass of air- the pitch will become higher but only until the aircraft loses the energy it gained from the pitch up- after which it will retain it's original attitude and continue climbing with the same rate of climb- because after some time the pitch angle wouldn't hold the speed as the aircraft transitions to flying in the new "air mass".
Elaborating on the concept of fixed thrust: These aircraft are built in a way that they maintain a uniform setting of thrust throughout the whole duration of the climb, decided after their performance calculations. Meaning- if there is a change in a headwind- they will pitch a little bit higher. This is possible due to the logic of the machine that rotates and keeps a velocity higher than V2, which is the safe airborn speed- meaning there is a margin.
Next: as for sudden decreasing headwinds- the aircraft always corrects it's pitch accordingly, and they are not as edgy as little light planes. Finally- the pilots can always lower the nose or apply more thrust or both. In addition- when conditions prevail that dictate the usage of wind shear conditions in the calculations- the aircraft is rotated at a higher velocity than the normal V2, giving it further margin, and they usually use flaps 20 (or the equivalent in an airbus which I am not familiar with) in order to support further fluctuations in wind speed. All in all- the aircraft has margins.
As for the actual technique the plane maintains pitch- I would assume that it has its barriers and the fluctuations in attitude are gentle enough in order not to get to high or low exactly for the reason you mentioned above. If you maintain a constant pitch attitude- you can also exceed the flaps speed. Final note- when encountering a real wind shear- 15 knots deviation, 5 degrees of pitch fluctuation, 1 dot of GS deviation, 500 FPM vertical speed deviation, the pilots would engage the wind shear maneuver- meaning TOGA (initiating a sequence of actions that are built to sustain a wind shear situation), full thrust to maintain possitive vertical speed until clear.
I hope this is not too technical, will be happy to explain everything. I you understand the reason the aircraft acted the way it acted- maybe you will be able to point out exactly how it felt.
It was due to the wind shear. Wind shear creates a vector gradient. If the vector gradient direction is upward in the head you'll get additional vertical force for lifting and its magnitude is larger than the downward force in the tail. That's why it's called wind shear because the wind applies a shear force to a flying body (in this case airplane). That's will happen only when the high-speed wind is heading towards your plane and your plane take off with a rotational velocity (Vr) designed for a steady condition. As force can be modeled as a rate of change of momentum over time it makes sense that you get a sudden steep climbing pattern because the momentum of your plane has been increased.
Wind shear is classified as an atmospheric disturbance. Therefore, it is correlated directly to the flight qualities. You can check the table in Flight Dynamic Principle Chapter 14 to see the relationship. As long as you can maintain control there will be no problem. For the passenger's complaint, they have the right to complaints as a part of the whole system. A complaint is a gift to improve the overall system the airlines, the pilot skills, and the aircraft manufacturers.
The only thing to be concerned from your case is communications. You should get a weather report before take off. Someday, this communication issue can be reduced by visualizing the wind. I guess everybody would be happy if we are able to see the wind shear. Some airports have the technology to visualize wind shear. It's just the implementation of the Tyndall effect (at least for a while). Maybe in the future, everyone will able to see the wind shear using 3D light technology. The plasma emission technology is the one and only 3D light that we have today and it's dangerous. The plasma emission phenomenon near the cloud full of static electric charge will transform your Airplane to a giant spark plug. For now, just trust the pilot they're trained well. If you're a pilot just trust the aircraft manufacturers they've been work so hard to keep everybody safe and of course, communicate well with the ATC & ground staff.
